PageSpeed Optimization Master Index

Complete Guide Suite for 100%+ Performance Coverage

📚 DOCUMENT SUITE OVERVIEW

This comprehensive PageSpeed optimization suite consists of four interconnected documents designed to support developers and DevOps teams in achieving optimal web performance across mobile and desktop platforms.

Document Hierarchy

┌─────────────────────────────────────────────────────┐
│           MASTER INDEX (This Document)              │
│         Navigation & Overview of All Resources      │
└─────────────────────────────────────────────────────┘
                         │
         ┌───────────────┼───────────────┐
         │               │               │
         ▼               ▼               ▼
┌─────────────┐  ┌──────────────┐  ┌──────────────┐
│  CHECKLIST  │  │ IMPLEMENTATION│  │ QUICK REF    │
│   Complete  │  │     Guide     │  │  Cheat Sheet │
│   Coverage  │  │   Tactical    │  │   Rapid      │
│   Reference │  │   Code & How  │  │   Access     │
└─────────────┘  └──────────────┘  └──────────────┘

📝 DOCUMENT MAP

Master Index (You are here)
├── Quick Start Guide
├── How to Use This Suite
├── Learning Paths
├── Workflow Integration
├── Metrics & Monitoring
├── Tools Reference
├── Success Criteria
├── Common Scenarios
├── Troubleshooting
└── Additional Resources

PageSpeed Universal Optimization Checklist
├── Core Web Vitals (11 sub-sections)
├── Performance (6 major sections, 20+ sub-sections)
├── Accessibility (4 sections)
├── Best Practices (4 sections)
├── SEO (5 sections)
├── Testing & Monitoring (4 sections)
├── Mobile Optimization
├── Desktop Optimization
├── Progressive Enhancement
├── Visual Optimization
└── Analytics & Measurement

Implementation Guide
├── Quick Start (Priority Matrix)
├── Compression Setup
├── Image Optimization (with tools)
├── Lazy Loading (code examples)
├── Critical CSS (extraction methods)
├── JavaScript Optimization
├── Font Optimization
├── Caching Configuration
├── Resource Hints
├── Third-Party Optimization
├── Web Vitals Monitoring
├── Build Process
└── Continuous Monitoring Setup

Quick Reference Cheat Sheet
├── Core Web Vitals Targets
├── Top 10 Quick Wins
├── Image Commands
├── Code Templates
├── Cache Headers
├── Testing Commands
├── Optimization Checklists
├── Common Issues & Fixes
├── Performance Budgets
├── SEO Quick Checks
├── Accessibility Quick Checks
└── Essential Tools

📖 DOCUMENT 1: Universal Optimization Checklist

File: PageSpeed_Universal_Optimization_Checklist.md

Purpose: Comprehensive, atomic, MECE checklist covering all aspects of PageSpeed optimization

Best Used For:

Complete audit of website performance
Planning optimization initiatives
Tracking progress across categories
Ensuring nothing is missed
Team alignment on standards

Structure:

11 major categories with 100+ checklist items
Performance threshold references
Success criteria definitions
Resource links and documentation
Implementation roadmap (4-phase approach)

Key Sections:

Core Web Vitals Optimization
Performance Optimization
Accessibility Optimization
Best Practices Optimization
SEO Optimization
Testing & Monitoring
Mobile-Specific Optimization
Desktop-Specific Optimization
Progressive Enhancement
Visual Optimization
Analytics & Measurement

📖 DOCUMENT 2: Implementation Guide

File: PageSpeed_Implementation_Guide.md

Purpose: Step-by-step tactical instructions with code examples

Best Used For:

Actually implementing optimizations
Copy-paste code snippets
Configuration templates
Build process setup
Understanding how to execute each optimization

Structure:

12 implementation sections
Real code examples for every optimization
Configuration files (Nginx, Apache, Webpack, Next.js)
Priority matrix for quick wins
Automation scripts and tools

Key Sections:

Compression Setup
Image Optimization
Lazy Loading Implementation
Critical CSS Extraction
JavaScript Optimization
Font Optimization
Caching Configuration
Resource Hints
Third-Party Optimization
Web Vitals Monitoring
Build Process Optimization
Continuous Monitoring

📖 DOCUMENT 3: Quick Reference Cheat Sheet

File: PageSpeed_Quick_Reference_Cheat_Sheet.md

Purpose: Rapid-access reference for most common optimizations

Best Used For:

Quick lookups during development
Emergency fixes
Onboarding new team members
Daily development reference
Print and keep at desk

Structure:

Top 10 quick wins
Essential code snippets
Command line references
Common issue troubleshooting
Testing commands
Deployment checklist

Key Sections:

Core Web Vitals targets
Top 10 quick wins
Image optimization commands
Critical templates (responsive images, fonts, caching)
Common issues & fixes
Performance budgets
Essential tools list

🎯 HOW TO USE THIS SUITE

For New Projects

Phase 1: Planning

Review the Checklist to understand full scope
Review the Implementation Guide priority matrix
Establish performance budgets from Cheat Sheet
Set up baseline metrics

Phase 2: Foundation

Use Cheat Sheet "Top 10 Quick Wins"
Follow Implementation Guide Week 1 checklist
Track progress in Checklist document
Verify with testing tools

Phase 3: Core Optimizations

Use Implementation Guide sections 1-9
Reference Checklist for completeness
Use Cheat Sheet for quick code lookups
Continuous testing and validation

Phase 4: Advanced & Monitoring

Complete remaining Checklist items
Implement monitoring from Implementation Guide sections 10-12
Establish continuous improvement process
Document team processes

For Existing Projects

Audit Phase

Run Lighthouse and PageSpeed Insights
Use Checklist to identify gaps
Prioritize issues by impact

Quick Fixes

Implement Cheat Sheet "Top 10 Quick Wins"
Focus on highest-impact, lowest-effort items
Verify improvements immediately

**Systematic Improvement

Follow Implementation Guide systematically
Track progress with Checklist
Use Cheat Sheet for reference
Measure before/after for each change

For Ongoing Maintenance

Daily Development

Keep Cheat Sheet accessible
Reference for common patterns
Quick issue resolution

Weekly/Sprint Reviews

Monitor Core Web Vitals
Check Checklist for regression
Address new issues promptly

Monthly Audits

Full Checklist review
Update performance budgets
Review monitoring data
Plan improvements

🎓 LEARNING PATH

Beginner Level

Start with:

Cheat Sheet - Learn the basics and quick wins
Core Web Vitals section of Checklist
Top 10 Quick Wins from Implementation Guide

Focus on:

Image optimization
Lazy loading
Basic caching
Minification

Intermediate Level

Start with:

Full Checklist review
Implementation Guide sections 1-6
Advanced patterns in Cheat Sheet

Focus on:

Code splitting
Critical CSS
Font optimization
Service workers (basics)

Advanced Level

Start with:

Complete Checklist audit
All Implementation Guide sections
Custom solutions beyond templates

Focus on:

Advanced service worker strategies
Custom build optimizations
Performance budgets and monitoring
Team education and processes

🔄 WORKFLOW INTEGRATION

Development Workflow

┌──────────────┐
│ Plan Feature │
└──────┬───────┘
       │
       ▼
┌──────────────────────┐
│ Reference Checklist  │  ← Check requirements
│ & Implementation     │
└──────┬───────────────┘
       │
       ▼
┌──────────────────────┐
│ Develop with         │  ← Use Cheat Sheet
│ Cheat Sheet Open     │    for quick reference
└──────┬───────────────┘
       │
       ▼
┌──────────────────────┐
│ Test Performance     │  ← Verify against
│ (Lighthouse)         │    Checklist criteria
└──────┬───────────────┘
       │
       ▼
┌──────────────────────┐
│ Fix Issues           │  ← Use Implementation
│                      │    Guide solutions
└──────┬───────────────┘
       │
       ▼
┌──────────────────────┐
│ Deploy & Monitor     │  ← Setup from
│                      │    Implementation Guide
└──────────────────────┘

Code Review Checklist

Reviewer should verify:

Images have width/height attributes (Cheat Sheet ref)
New images are lazy loaded appropriately
No render-blocking resources added
JavaScript is minified and code-split
Cache headers are appropriate
Performance budget not exceeded
Lighthouse score maintained or improved

Use: Quick Reference section in Cheat Sheet

CI/CD Integration

Pre-commit:

# Lint and format
npm run lint
npm run format

# Quick performance check
npm run lighthouse:quick

Pre-merge:

# Full Lighthouse audit
npm run lighthouse:full

# Bundle size check
npm run analyze:bundle

# Performance budget check
npm run check:budget

Post-deploy:

# Real User Monitoring alert setup
# Based on Implementation Guide Section 10

Reference: Implementation Guide Section 12 (Continuous Monitoring)

📊 METRICS TRACKING

Key Performance Indicators

Track these metrics from Checklist thresholds:

Core Web Vitals (Must Pass)

LCP: ≤2.5s (75th percentile)
CLS: ≤0.1 (75th percentile)
INP: ≤200ms (75th percentile)

Supporting Metrics

FCP: ≤1.8s
TTFB: ≤800ms
Speed Index: ≤3.4s
TBT: ≤200ms

Lighthouse Scores

Performance: 90+
Accessibility: 90+
Best Practices: 90+
SEO: 90+

Measurement Frequency

Real-time: Core Web Vitals via RUM Daily: Automated Lighthouse CI Weekly: PageSpeed Insights check Monthly: Full audit with Checklist

Setup: See Implementation Guide Section 10 & 12

🛠️ TOOLS REFERENCE

Essential Tools (From All Documents)

Testing & Audit

PageSpeed Insights: https://pagespeed.web.dev/
Lighthouse CLI: npm install -g lighthouse
WebPageTest: https://www.webpagetest.org/
Chrome DevTools: Built-in

Image Optimization

Sharp: npm install sharp
Squoosh: https://squoosh.app/
ImageOptim: https://imageoptim.com/
Command-line tools (see Cheat Sheet)

Monitoring

web-vitals: npm install web-vitals
Google Search Console
Chrome UX Report (CrUX)
Custom RUM (see Implementation Guide)

Build Tools

Webpack Bundle Analyzer
Lighthouse CI: npm install -g @lhci/cli
Critical CSS: npm install critical

Analysis

Tool Selection Guide

For quick analysis: PageSpeed Insights + Chrome DevTools For deep analysis: WebPageTest + Lighthouse CLI For monitoring: web-vitals + Custom RUM For CI/CD: Lighthouse CI For images: Sharp (automation) or Squoosh (manual)

🎯 SUCCESS CRITERIA

Definition of Done

A website is considered optimized when:

✅ Core Web Vitals

All three metrics pass at 75th percentile
Based on 28 days of field data
Both mobile and desktop

✅ Lighthouse Scores

All categories score 90+
Tested on both mobile and desktop
No high-severity issues

✅ Checklist Coverage

95%+ of applicable items completed
Documented exceptions with reasoning
Regular review schedule established

✅ Monitoring Active

Real User Monitoring implemented
Alerts configured
Regular reporting in place
Team trained on metrics

✅ Process Integration

Performance budgets set
CI/CD checks active
Code review includes performance
Documentation updated

📋 COMMON SCENARIOS

Scenario 1: New E-commerce Site

Priority Focus:

Product images (largest performance impact)
LCP optimization (hero images)
Third-party scripts (analytics, payment)
Mobile performance

Document Flow:

Checklist - Category 1 (Core Web Vitals) & 2 (Performance)
Implementation Guide - Sections 2, 3, 5, 9
Cheat Sheet - Image optimization, lazy loading

Scenario 2: News/Blog Site

Priority Focus:

Text content (fonts, typography)
Article images
Ad performance
Multiple page templates

Document Flow:

Checklist - Category 2 (Performance) & 5 (SEO)
Implementation Guide - Sections 4, 6, 9
Cheat Sheet - Critical CSS, fonts, caching

Scenario 3: Single Page Application (SPA)

Priority Focus:

JavaScript bundle size
Code splitting
Initial load performance
Route-based optimization

Document Flow:

Checklist - Category 2 (Performance) & 9 (Progressive Enhancement)
Implementation Guide - Sections 5, 11
Cheat Sheet - JS optimization, code splitting

Scenario 4: Marketing/Landing Page

Priority Focus:

First impression (LCP)
Form performance
Video/media
Conversion tracking

Document Flow:

Checklist - Category 1 (Core Web Vitals)
Implementation Guide - Sections 2, 3, 9
Cheat Sheet - Quick wins, YouTube facade

🔍 TROUBLESHOOTING INDEX

Poor LCP Score

Diagnosis:

Identify LCP element using Chrome DevTools
Check if image or text
Measure TTFB

Solutions:

Checklist Section 1.1 (LCP Optimization)
Implementation Guide Section 2 (Images)
Cheat Sheet LCP checklist

Common Fixes:

Optimize LCP image format and size
Preload LCP element
Eliminate render-blocking resources
Reduce server response time

High CLS Score

Diagnosis:

Use Layout Shift Regions in DevTools
Identify shifting elements
Check image dimensions and ad slots

Solutions:

Checklist Section 1.2 (CLS Optimization)
Implementation Guide Section 2.2 (Images), 6 (Fonts)
Cheat Sheet CLS checklist

Common Fixes:

Add width/height to all images
Reserve space for ads/embeds
Preload fonts with font-display: swap
Use transform for animations

High INP Score

Diagnosis:

Check for long tasks in DevTools
Identify slow event handlers
Measure third-party script impact

Solutions:

Checklist Section 1.3 (INP Optimization)
Implementation Guide Section 5 (JavaScript)
Cheat Sheet INP checklist

Common Fixes:

Break up long tasks
Defer non-critical JavaScript
Optimize third-party scripts
Use debounce/throttle

Low Lighthouse Performance Score

Diagnosis:

Review Lighthouse opportunities
Check diagnostics section
Identify highest-impact issues

Solutions:

Checklist - Full Category 2 review
Implementation Guide - Systematic approach
Cheat Sheet - Quick wins first

Common Fixes:

Optimize images (usually biggest impact)
Eliminate render-blocking resources
Enable text compression
Minimize main-thread work

📞 GETTING HELP

When to Use Each Document

"I need to understand what to do" → Start with Checklist

"I know what to do, but not how" → Use Implementation Guide

"I need a quick fix now" → Check Cheat Sheet

"I'm not sure where to start" → Read this Master Index

Resource Escalation Path

Simple Question
    ↓
Cheat Sheet
    ↓
Still Unclear?
    ↓
Implementation Guide
    ↓
Still Need Help?
    ↓
Checklist (comprehensive)
    ↓
Still Stuck?
    ↓
External Resources:
- web.dev tutorials
- Chrome DevTools docs
- Stack Overflow
- Official documentation

🔄 DOCUMENT MAINTENANCE

Update Schedule

Monthly:

Review Core Web Vitals thresholds
Update tool versions
Add new optimization techniques
Incorporate team feedback

Quarterly:

Major revision check
New browser features
Updated best practices
Case study additions

Annually:

Complete document overhaul
Remove deprecated techniques
Major platform updates
Performance landscape changes

Version Control

Current versions of all documents are maintained together.

Current Version: 1.0
Last Updated: November 2025
Next Review: February 2026

📚 ADDITIONAL RESOURCES

Official Documentation

Learning Paths

Community

Tools & Services

SpeedCurve - RUM & Synthetic monitoring
Calibre - Performance monitoring
Cloudflare - CDN & optimization
Cloudinary - Image optimization

✅ QUICK START CHECKLIST

To get started with this document suite:

🎓 CERTIFICATION PATH

Self-Assessment Levels

Level 1: Basics (Can achieve 70-80 scores)

Understand Core Web Vitals
Can implement image optimization
Uses lazy loading
Enables basic caching
Mastery: Cheat Sheet memorized

Level 2: Intermediate (Can achieve 80-90 scores)

Implements code splitting
Extracts critical CSS
Optimizes fonts
Manages third-party scripts
Mastery: Implementation Guide completed

Level 3: Advanced (Can achieve 90+ scores)

Architects performance solutions
Implements custom monitoring
Establishes team processes
Teaches others
Mastery: Full Checklist expertise

Level 4: Expert (Consistent 95+ scores)

Innovates new solutions
Contributes to community
Writes custom tooling
Advises organizations
Mastery: All documents internalized + industry leadership

📈 SUCCESS METRICS

Individual Developer Metrics

Lighthouse scores of PRs
Performance budget compliance
Time to implement optimizations
Regression prevention

Team Metrics

Average site Lighthouse score
Core Web Vitals pass rate
Performance issue resolution time
Knowledge sharing sessions held

Business Metrics

Page load time impact on conversions
Mobile vs desktop performance gap
SEO ranking improvements
User engagement metrics

🏆 BEST PRACTICES SUMMARY

From across all documents:

Mobile First - Always optimize mobile first, desktop is easier
Measure Everything - You can't improve what you don't measure
Automate Testing - Manual testing doesn't scale
Set Budgets - Prevent performance regression
Optimize Images First - Usually the biggest wins
Lazy Load Smartly - Not above the fold
Critical CSS Only - Keep inline CSS minimal
Code Split Aggressively - Users don't need everything at once
Monitor Continuously - Performance degrades over time
Educate Team - Performance is everyone's responsibility

🎯 FINAL RECOMMENDATIONS

For Maximum Impact

Week 1: Implement all items from Cheat Sheet "Top 10 Quick Wins"
Week 2-3: Work through Implementation Guide systematically
Week 4: Complete remaining Checklist items
Ongoing: Monitor with tools from Implementation Guide Section 10-12

For Best Results

Don't skip the planning phase
Measure before and after every change
Test on real devices and networks
Document what works for your team
Share knowledge across the organization
Review and update quarterly

For Long-term Success

Integrate performance into development culture
Make it part of code review
Automate everything possible
Celebrate performance wins
Learn from performance issues
Stay updated with industry changes

Remember: Web performance is a journey, not a destination. These documents provide the roadmap, but continuous improvement and monitoring are essential for long-term success.

Document Suite Version: 1.0
Master Index Version: 1.0
Last Updated: November 2025
Next Review: February 2026

Maintained by: Your Development Team
Questions? Reference the appropriate document or external resources listed above

End of Master Index

Universal PageSpeed Mobile & Desktop Optimization Checklist

Comprehensive ATOMIC-MECE Guide to 100%+ Performance Coverage

📊 PERFORMANCE THRESHOLDS REFERENCE

Core Web Vitals Targets (75th Percentile)

Metric	Good	Needs Improvement	Poor
LCP (Largest Contentful Paint)	≤2.5s	2.5-4.0s	>4.0s
CLS (Cumulative Layout Shift)	≤0.1	0.1-0.25	>0.25
INP (Interaction to Next Paint)	≤200ms	200-500ms	>500ms

Additional Performance Metrics

Metric	Good	Needs Improvement	Poor
FCP (First Contentful Paint)	≤1.8s	1.8-3.0s	>3.0s
TTFB (Time to First Byte)	≤800ms	800-1800ms	>1800ms
Speed Index	≤3.4s	3.4-5.8s	>5.8s
TBT (Total Blocking Time)	≤200ms	200-600ms	>600ms
TTI (Time to Interactive)	≤3.8s	3.8-7.3s	>7.3s

Lighthouse Score Ranges

Good: 90-100
Needs Improvement: 50-89
Poor: 0-49

Resource: Web Vitals Initiative

🎯 CATEGORY 1: CORE WEB VITALS OPTIMIZATION

1.1 Largest Contentful Paint (LCP) Optimization

1.1.1 Server Response Time (TTFB)

Optimize server infrastructure
- Target: TTFB ≤800ms
- Use CDN for static assets
- Implement caching strategies (Redis, Memcached)
- Optimize database queries
- Resource: Optimize TTFB
Enable HTTP/2 or HTTP/3
- Multiplexing support for parallel requests
- Header compression
- Server push capabilities

1.1.2 Resource Load Delay

Eliminate render-blocking resources
- Defer non-critical JavaScript
- Inline critical CSS (<14KB)
- Use media attributes for non-critical CSS
- Resource: Eliminate render-blocking resources
Optimize Critical Rendering Path
- Minimize critical resource count
- Reduce critical resource size
- Shorten critical path length

1.1.3 Resource Load Time

Optimize images for LCP
- Use appropriate formats (WebP, AVIF)
- Implement responsive images with srcset
- Compress images (aim for <200KB for hero images)
- Priority hint: <img fetchpriority="high">
- Resource: Optimize LCP
Preload critical resources
- <link rel="preload"> for LCP image/font
- Preconnect to required origins
- DNS prefetch for third-party domains

1.1.4 Client-Side Rendering Delay

Minimize JavaScript execution time
- Code splitting and lazy loading
- Tree shaking unused code
- Use web workers for heavy computations
- Target: Main thread work <3.8s

1.2 Cumulative Layout Shift (CLS) Optimization

1.2.1 Images Without Dimensions

Set explicit width and height attributes
- Add width/height to all <img> tags
- Use aspect-ratio CSS for responsive images
- Reserve space with aspect-ratio boxes
- Resource: Optimize CLS

1.2.2 Ads, Embeds, and Iframes

Reserve space for dynamic content
- Define minimum dimensions for ad slots
- Use placeholder for embeds
- Set aspect ratios for iframes

1.2.3 Dynamically Injected Content

Load content above the fold statically
- Avoid inserting content above existing content
- Use transform animations instead of layout properties
- Preload and reserve space for web fonts

1.2.4 Web Fonts Causing FOIT/FOUT

Optimize font loading strategy
- Use font-display: swap or optional
- Preload critical fonts
- Self-host fonts when possible
- Subset fonts to include only needed characters
- Resource: Font best practices

1.2.5 Animations

Use transform and opacity only
- Avoid animating: top, left, width, height, margin
- Use CSS transforms (translateX/Y, scale, rotate)
- Use will-change sparingly

1.3 Interaction to Next Paint (INP) Optimization

1.3.1 JavaScript Execution Time

Minimize main thread blocking
- Break up long tasks (>50ms)
- Use requestIdleCallback for non-urgent work
- Implement code splitting
- Reduce JavaScript payload
- Resource: Optimize INP

1.3.2 Event Handler Optimization

Optimize interaction handlers
- Debounce/throttle frequent events
- Use passive event listeners
- Avoid forced synchronous layouts
- Minimize DOM manipulation

1.3.3 Rendering Work

Reduce render complexity
- Simplify CSS selectors
- Reduce scope and complexity of style calculations
- Minimize layout thrashing
- Use CSS containment

1.3.4 Third-Party Scripts

Audit and optimize third-party impact
- Load third-party scripts asynchronously
- Use facade patterns for heavy embeds
- Implement third-party script loading strategy
- Monitor third-party performance budget

⚡ CATEGORY 2: PERFORMANCE OPTIMIZATION

2.1 JavaScript Optimization

2.1.1 Payload Reduction

Minimize JavaScript bundle size
- Target: <300KB gzipped for initial bundle
- Remove unused code (tree shaking)
- Analyze bundle with webpack-bundle-analyzer
- Split code by route/component
- Resource: Reduce JavaScript payloads
Minify and compress JavaScript
- Use Terser or esbuild for minification
- Enable gzip/brotli compression
- Remove console logs in production

2.1.2 Loading Strategy

Implement proper loading patterns
- Use async for independent scripts
- Use defer for DOM-dependent scripts
- Inline critical JavaScript (<2KB)
- Load non-critical scripts after main content
Leverage code splitting
- Route-based splitting
- Component-based lazy loading
- Dynamic imports for heavy features
- Vendor bundle separation

2.1.3 Execution Optimization

Optimize JavaScript execution
- Avoid long tasks (>50ms)
- Use Web Workers for CPU-intensive tasks
- Implement virtual scrolling for long lists
- Debounce expensive operations
- Resource: Optimize JavaScript execution
Reduce JavaScript boot-up time
- Parse and compile cost reduction
- Minimize polyfills (use module/nomodule pattern)
- Use modern JavaScript (ES2015+) for modern browsers

2.1.4 Framework-Specific

React optimization
- Use React.lazy() and Suspense
- Implement React.memo for expensive components
- Use useMemo and useCallback appropriately
- Avoid inline function definitions in render
Vue optimization
- Use async components
- Implement v-once for static content
- Use v-show vs v-if appropriately
Angular optimization
- Use OnPush change detection
- Implement lazy loading for modules
- Use trackBy for ngFor

2.2 CSS Optimization

2.2.1 Delivery Optimization

Eliminate render-blocking CSS
- Inline critical CSS (<14KB)
- Load non-critical CSS asynchronously
- Use media queries to defer non-matching CSS
- Resource: Extract critical CSS
Minimize CSS payload
- Remove unused CSS (PurgeCSS, UnCSS)
- Minify CSS
- Target: <50KB critical CSS

2.2.2 CSS Architecture

Optimize CSS selectors
- Reduce selector complexity
- Avoid universal selectors
- Minimize nesting depth (<3 levels)
- Use specific selectors over descendant
Use efficient CSS properties
- Prefer CSS transforms over layout properties
- Use CSS containment
- Avoid expensive properties (box-shadow, filter on large areas)
- Use will-change sparingly

2.2.3 CSS Loading

Optimize font loading
- Use font-display: swap or optional
- Preload critical fonts
- Subset fonts
- Use variable fonts when appropriate
Use CSS preprocessing efficiently
- Remove unused mixins and variables
- Optimize output configuration
- Use CSS variables for theming

2.3 Image Optimization

2.3.1 Format and Compression

Use next-gen image formats
- WebP for broad support
- AVIF for best compression (with WebP fallback)
- Progressive JPEG for large images
- Resource: Serve images in next-gen formats
Properly size images
- Serve responsive images (srcset, sizes)
- Match image dimensions to display size
- Target: No images >2x display size
- Resource: Properly size images
Compress images efficiently
- Target compression: 85-90% quality for JPEG
- Use tools: ImageOptim, Squoosh, Sharp
- Automate with build process
- Target: Hero images <200KB, other images <100KB

2.3.2 Loading Strategy

Implement lazy loading
- Use native lazy loading: loading="lazy"
- Lazy load offscreen images
- Eager load above-the-fold images
- Resource: Browser-level lazy loading
Prioritize critical images
- Use fetchpriority="high" for LCP image
- Preload hero images
- Avoid lazy loading above-the-fold images

2.3.3 Delivery Optimization

Use CDN for images
- Image CDN with automatic optimization
- Dynamic resizing and format selection
- Consider: Cloudinary, Imgix, Cloudflare Images
Implement responsive images
- Use srcset for resolution switching
- Use picture element for art direction
- Provide appropriate sizes attribute

2.4 Font Optimization

2.4.1 Loading Strategy

Optimize font loading
- Preload critical fonts
- Use font-display: swap (or optional for body text)
- Limit number of font weights and styles
- Resource: Best practices for fonts
Self-host fonts when possible
- Reduce DNS lookups
- Better caching control
- Eliminate third-party requests

2.4.2 Font Files

Optimize font files
- Use WOFF2 format (best compression)
- Subset fonts (include only needed characters)
- Use variable fonts to reduce file count
- Target: <50KB per font file
Limit font usage
- Maximum 2-3 font families
- Limit to essential weights and styles
- Use system fonts for non-critical text

2.5 Network and Caching

2.5.1 Caching Strategy

Implement effective caching headers
- Long cache for immutable assets (1 year)
- Use cache-busting for versioned files
- Implement stale-while-revalidate
- Resource: HTTP caching

Cache-Control headers

Static assets: Cache-Control: public, max-age=31536000, immutable
HTML: Cache-Control: no-cache
API: Cache-Control: private, max-age=3600

2.5.2 Service Worker

Implement service worker
- Cache static assets
- Implement offline fallback
- Use workbox for easier implementation
- Resource: Service workers

2.5.3 Resource Hints

Use resource hints strategically
- Preconnect to critical third-party origins
- DNS-prefetch for third-party domains
- Preload critical resources
- Prefetch for likely navigation
- Resource: Resource hints

2.5.4 Compression

Enable text compression
- Enable Brotli compression (level 4-6)
- Fallback to gzip (level 6-9)
- Compress all text assets (HTML, CSS, JS, JSON, SVG)
- Resource: Enable text compression

2.6 Third-Party Resources

2.6.1 Third-Party Scripts

Audit third-party impact
- Identify blocking third-party scripts
- Measure performance impact
- Remove unnecessary third-party code
- Resource: Third-party JavaScript
Optimize third-party loading
- Load asynchronously
- Use facades for heavy embeds (YouTube, maps)
- Implement lazy loading for below-fold embeds
- Self-host when beneficial

2.6.2 Analytics and Tracking

Optimize analytics implementation
- Load analytics asynchronously
- Use minimal tracking code
- Consider server-side analytics
- Batch analytics events

2.7 Server and Hosting

2.7.1 Server Configuration

Optimize server response time
- Target: TTFB <800ms
- Use fast hosting infrastructure
- Implement server-side caching
- Optimize database queries
Enable HTTP/2 or HTTP/3
- Multiplexing benefits
- Header compression
- Server push for critical resources

2.7.2 Content Delivery

Use CDN effectively
- Global edge network
- Automatic asset optimization
- DDoS protection
- Consider: Cloudflare, Fastly, AWS CloudFront
Implement edge caching
- Cache static assets at edge
- Use edge workers for dynamic content
- Implement stale-while-revalidate

♿ CATEGORY 3: ACCESSIBILITY OPTIMIZATION

3.1 Perceivable Content

3.1.1 Images and Media

Provide alt text for images
- Descriptive alt text for informative images
- Empty alt="" for decorative images
- No "image of" or "picture of" prefixes
- Resource: Image accessibility
Ensure sufficient color contrast
- Minimum 4.5:1 for normal text
- Minimum 3:1 for large text (18pt+)
- Use contrast checker tools
- Resource: Color contrast
Provide captions and transcripts
- Captions for video content
- Transcripts for audio content
- Synchronized captions

3.1.2 Text and Typography

Use legible font sizes
- Minimum 16px for body text
- Scalable text (no fixed pixel heights)
- Responsive typography
Avoid text in images
- Use actual text instead of images of text
- Exception: logos and essential graphics

3.2 Operable Interface

3.2.1 Keyboard Navigation

Ensure full keyboard accessibility
- All interactive elements keyboard accessible
- Logical tab order
- Visible focus indicators
- No keyboard traps
- Resource: Keyboard access
Provide skip navigation
- Skip to main content link
- Skip repetitive navigation blocks

3.2.2 Touch Targets

Adequate touch target size
- Minimum 48×48px for mobile
- Minimum 44×44px for desktop
- Sufficient spacing between targets (8px)
- Resource: Touch targets

3.3 Understandable Content

3.3.1 Semantic HTML

Use proper HTML structure
- Semantic elements (header, nav, main, article, aside, footer)
- Proper heading hierarchy (h1-h6)
- Meaningful landmark roles
- Resource: Semantic HTML
Proper form labels
- Label elements for all inputs
- Descriptive labels
- Associated with inputs (for/id)
- Resource: Form labels

3.3.2 Language and Readability

Declare document language
- <html lang="en"> attribute
- Use appropriate language codes
- Resource: Document language
Clear and simple language
- Appropriate reading level
- Clear instructions
- Descriptive link text

3.4 Robust Implementation

3.4.1 ARIA Usage

Implement ARIA correctly
- Use native HTML when possible
- ARIA only when necessary
- Valid ARIA attributes
- No conflicting ARIA roles
- Resource: ARIA practices
Provide ARIA labels
- aria-label for icon buttons
- aria-labelledby for complex widgets
- aria-describedby for additional context

3.4.2 Focus Management

Manage focus appropriately
- Focus on modal open
- Focus trap in modals
- Return focus on modal close
- Visible focus indicators

🔒 CATEGORY 4: BEST PRACTICES OPTIMIZATION

4.1 Security

4.1.1 HTTPS

Use HTTPS exclusively
- Valid SSL certificate
- Redirect HTTP to HTTPS
- HSTS header enabled
- No mixed content
- Resource: HTTPS best practices

4.1.2 Content Security Policy

Implement CSP
- Define trusted content sources
- Prevent XSS attacks
- Use nonce or hash for inline scripts
- Resource: Content Security Policy

4.1.3 Permissions and APIs

Request permissions appropriately
- Only request needed permissions
- Request at time of use
- Provide context for requests

4.2 Code Quality

4.2.1 JavaScript

Avoid console errors
- No JavaScript errors in console
- Remove console.log in production
- Proper error handling
Use modern JavaScript
- ES2015+ features
- Avoid deprecated APIs
- Use strict mode

4.2.2 Frameworks and Libraries

Keep dependencies updated
- Regular security updates
- Latest stable versions
- Audit for known vulnerabilities
- Resource: npm audit
Avoid known vulnerable libraries
- Regular security scans
- Replace vulnerable dependencies
- Monitor security advisories

4.3 Browser Compatibility

4.3.1 Cross-browser Support

Test across browsers
- Chrome, Firefox, Safari, Edge
- Mobile browsers (iOS Safari, Chrome Android)
- Use feature detection, not browser detection
Provide fallbacks
- Progressive enhancement
- Polyfills for missing features
- Graceful degradation

4.3.2 Standards Compliance

Use standards-compliant code
- Valid HTML
- Valid CSS
- Standard JavaScript APIs

4.4 User Experience

4.4.1 Visual Stability

Prevent layout shifts
- Reserve space for dynamic content
- Fixed dimensions for images/ads
- Avoid inserting content above viewport

4.4.2 Performance Perception

Implement loading states
- Skeleton screens
- Progress indicators
- Smooth transitions
- Optimistic UI updates

🔍 CATEGORY 5: SEO OPTIMIZATION

5.1 Content Optimization

5.1.1 Metadata

Provide descriptive title
- Unique title per page
- 50-60 characters
- Include primary keywords
- Format: "Page Title | Site Name"
- Resource: Document title
Write compelling meta descriptions
- 150-160 characters
- Include target keywords
- Unique per page
- Action-oriented
- Resource: Meta description
Use Open Graph tags
- og:title, og:description, og:image
- Twitter card tags
- Optimize for social sharing

5.1.2 Structured Data

Implement schema markup
- Use JSON-LD format
- Relevant schema types (Article, Product, FAQ, etc.)
- Validate with Schema.org validator
- Resource: Structured data
Rich snippets optimization
- Product schema with reviews
- Article schema with publication date
- FAQ schema for common questions

5.2 Crawlability

5.2.1 Indexing

Ensure pages are indexable
- No "noindex" on important pages
- No blocking in robots.txt
- Check robot meta tags
- Resource: Crawlable links
Create and submit sitemap
- XML sitemap with all important pages
- Submit to Google Search Console
- Update regularly
- Include lastmod dates

5.2.2 Robots.txt

Optimize robots.txt
- Allow crawling of important pages
- Block irrelevant pages
- Include sitemap location
- Resource: Robots.txt

5.3 Link Structure

5.3.1 Internal Linking

Use descriptive anchor text
- Avoid "click here" or generic text
- Describe destination page
- Use keywords naturally
- Resource: Descriptive link text
Ensure links are crawlable
- Use <a href=""> tags (not JavaScript-only)
- Valid href attributes
- No broken links
- Resource: Crawlable links

5.3.2 Canonicalization

Implement canonical URLs
- Self-referencing canonical on each page
- Resolve duplicate content issues
- Use absolute URLs
- Resource: Canonical links
Set up hreflang for multilingual sites
- Indicate language/region variations
- Bi-directional references
- Use correct language codes
- Resource: Hreflang

5.4 Mobile Optimization

5.4.1 Mobile-Friendly Design

Use responsive design
- Viewport meta tag configured
- Mobile-friendly layouts
- Readable font sizes (16px+)
- Resource: Mobile-friendly test
Avoid mobile usability issues
- No Flash content
- Adequate tap target sizes
- No horizontal scrolling
- Content sized to viewport

5.5 Technical SEO

5.5.1 HTTP Status

Return appropriate status codes
- 200 for successful pages
- 301 for permanent redirects
- 404 for not found
- Avoid soft 404s
- Resource: HTTP status codes

5.5.2 Page Performance

Maintain good Core Web Vitals
- Pass Core Web Vitals assessment
- Monitor field data regularly
- Fix performance issues promptly

🧪 CATEGORY 6: TESTING & MONITORING

6.1 Performance Testing

6.1.1 Lab Testing

Regular Lighthouse audits
- Test on mobile and desktop
- Use CI/CD integration
- Set performance budgets
- Resource: Lighthouse CI
Test with throttling
- Slow 3G network simulation
- CPU throttling (4x slowdown)
- Mid-tier device simulation (Moto G4)

6.1.2 Real User Monitoring

Implement RUM
- Track Core Web Vitals
- Monitor 75th percentile values
- Segment by device, connection, geography
- Resource: Web Vitals library
Use PageSpeed Insights regularly
- Check field data (CrUX)
- Monitor both origin and URL-level data
- Track trends over time

6.2 Continuous Optimization

6.2.1 Performance Budgets

Set and enforce budgets
- JavaScript bundle size limits
- Image size limits
- Total page weight limits
- Timing metric budgets
- Resource: Performance budgets
Automated budget monitoring
- CI/CD integration
- Fail builds that exceed budgets
- Alert on regression

6.2.2 A/B Testing

Test optimization impact
- Measure before and after
- Test with real users
- Monitor business metrics
- Iterate based on data

6.3 Cross-Device Testing

6.3.1 Device Testing

Test on actual devices
- iOS devices (iPhone, iPad)
- Android devices (various manufacturers)
- Different screen sizes
- Different browsers
Use device emulation
- Chrome DevTools device mode
- BrowserStack or similar
- Test touch interactions
- Test orientation changes

6.4 Monitoring Tools

6.4.1 Essential Tools

Google PageSpeed Insights
- Field and lab data
- Mobile and desktop
- Resource: PageSpeed Insights
Google Search Console
- Core Web Vitals report
- Mobile usability report
- Indexing status
- Resource: Search Console
Chrome UX Report
- Historical field data
- Origin-level aggregation
- BigQuery integration
- Resource: CrUX

6.4.2 Additional Tools

WebPageTest
- Detailed waterfall analysis
- Filmstrip view
- Multiple location testing
- Resource: WebPageTest
Lighthouse CI
- Automated testing
- GitHub integration
- Performance tracking
- Resource: Lighthouse CI

📱 CATEGORY 7: MOBILE-SPECIFIC OPTIMIZATION

7.1 Mobile Network Considerations

Optimize for slower networks
- Test on 3G/4G networks
- Implement adaptive loading
- Use connection-aware code (Network Information API)
- Provide offline functionality
Reduce data usage
- Compress all assets
- Lazy load images and video
- Use data-saver-friendly patterns
- Optimize video streaming

7.2 Mobile-Specific Features

Touch optimization
- Adequate touch targets (48×48px minimum)
- Implement touch feedback
- Support common gestures
- Avoid hover-dependent UI
Mobile viewport configuration
- <meta name="viewport" content="width=device-width, initial-scale=1">
- No user-scalable=no (unless absolutely necessary)
- Prevent zoom on input focus
Mobile-first CSS
- Start with mobile styles
- Use min-width media queries
- Progressive enhancement
- Conditional loading of desktop assets

🖥️ CATEGORY 8: DESKTOP-SPECIFIC OPTIMIZATION

8.1 Desktop Performance

Optimize for desktop capabilities
- Leverage higher bandwidth
- Provide enhanced experiences
- Use higher resolution images
- Enable advanced features
Desktop-specific features
- Hover states and interactions
- Keyboard shortcuts
- Multi-column layouts
- Advanced animations

8.2 Responsive Breakpoints

Design for common desktop sizes
- 1920×1080 (Full HD)
- 1366×768
- 1440×900
- 1280×720
- Support ultra-wide monitors

🔄 CATEGORY 9: PROGRESSIVE ENHANCEMENT

9.1 Core Functionality

Ensure baseline functionality
- Core features work without JavaScript
- Content accessible with CSS disabled
- Graceful degradation
- Progressive enhancement approach

9.2 Advanced Features

Layer enhancements progressively
- Feature detection (not browser detection)
- Polyfills for older browsers
- Modern features for capable browsers
- Use @supports for CSS features

🎨 CATEGORY 10: VISUAL OPTIMIZATION

10.1 Above-the-Fold Optimization

Prioritize visible content
- Inline critical CSS
- Preload hero images
- Defer below-the-fold resources
- Eliminate render-blocking resources

10.2 Visual Feedback

Provide instant feedback
- Loading indicators
- Skeleton screens
- Smooth transitions
- Progress feedback

📊 CATEGORY 11: ANALYTICS & MEASUREMENT

11.1 Web Vitals Tracking

Implement Web Vitals measurement

import {onCLS, onFCP, onLCP, onTTFB, onINP} from 'web-vitals';

onCLS(console.log);
onFCP(console.log);
onLCP(console.log);
onTTFB(console.log);
onINP(console.log);

Resource: web-vitals library

Send data to analytics
- Track in Google Analytics 4
- Custom analytics solution
- RUM service (SpeedCurve, Calibre, etc.)

11.2 Custom Metrics

Track business-specific metrics
- Time to key content
- Time to interactive for critical features
- Custom user timing marks
- Error tracking

🚀 IMPLEMENTATION ROADMAP

Phase 1: Quick Wins

Enable compression (Brotli/gzip)
Implement lazy loading for images
Add width/height to images
Minify CSS/JS
Optimize images (WebP, compression)
Add meta descriptions
Fix obvious accessibility issues

Phase 2: Core Optimizations

Implement code splitting
Optimize LCP element
Eliminate render-blocking resources
Implement effective caching
Add resource hints
Implement font optimization
Add structured data

Phase 3: Advanced Optimizations

Implement service worker
Optimize for INP
Third-party script optimization
Advanced image optimization (CDN, responsive images)
Implement performance monitoring
Set performance budgets
Advanced SEO optimizations

Phase 4: Continuous Improvement (Ongoing)

Monitor Core Web Vitals
Regular performance audits
A/B testing optimizations
Keep dependencies updated
Iterate based on real user data
Address new recommendations
Stay updated with best practices

🎯 SUCCESS CRITERIA

Core Web Vitals Passing

✅ LCP: ≤2.5s (75th percentile)
✅ CLS: ≤0.1 (75th percentile)
✅ INP: ≤200ms (75th percentile)

Lighthouse Scores

✅ Performance: 90+
✅ Accessibility: 90+
✅ Best Practices: 90+
✅ SEO: 90+

Additional Metrics

✅ FCP: ≤1.8s
✅ TTFB: ≤800ms
✅ Speed Index: ≤3.4s
✅ TBT: ≤200ms

📚 KEY RESOURCES

Official Documentation

Learning Resources

Testing Tools

Monitoring Services

🔧 AUTOMATION RECOMMENDATIONS

Suggested Automation Stack

// Example: Automated PageSpeed testing with Puppeteer/Playwright

const { chromium } = require('playwright');
const lighthouse = require('lighthouse');

async function runPageSpeedTest(url) {
  const browser = await chromium.launch();
  const { lhr } = await lighthouse(url, {
    port: new URL(browser.wsEndpoint()).port,
    output: 'json',
    onlyCategories: ['performance'],
  });
  
  // Extract Core Web Vitals
  const metrics = {
    lcp: lhr.audits['largest-contentful-paint'].numericValue,
    cls: lhr.audits['cumulative-layout-shift'].numericValue,
    tbt: lhr.audits['total-blocking-time'].numericValue,
    fcp: lhr.audits['first-contentful-paint'].numericValue,
  };
  
  await browser.close();
  return metrics;
}

CI/CD Integration

Run Lighthouse on every pull request
Fail builds that don't meet performance budgets
Generate performance reports
Track performance over time
Alert on regressions

Monitoring Setup

Real-time Core Web Vitals tracking
Daily performance reports
Alert on threshold violations
Geographic performance monitoring
Device-specific tracking

✅ FINAL CHECKLIST SUMMARY

Use this condensed checklist for quick reference:

Critical Path

Document Version: 1.0
Based on: Google PageSpeed Insights v5 Documentation
Last Updated: November 2025
Maintenance: Review quarterly and after major web platform updates

📝 NOTES FOR IMPLEMENTATION

Prioritization: Focus on Core Web Vitals first, as they have the most significant impact on user experience and SEO
Testing: Always test on real devices and networks, not just emulators
Iteration: Performance optimization is continuous—measure, optimize, measure again
Context: Some optimizations may not apply to all sites—use judgment based on your specific context
Trade-offs: Balance performance with functionality and business requirements
Documentation: Document all optimizations and their impact for future reference
Team Education: Ensure the entire team understands performance best practices

This checklist is a living document. As web standards and best practices evolve, update accordingly.

PageSpeed Optimization Implementation Guide

Tactical Step-by-Step Instructions with Code Examples

📋 QUICK START GUIDE

Priority Matrix

Priority	Optimization	Impact	Effort	Time to Implement
P0	Enable compression	High	Low	30 min
P0	Optimize images	High	Medium	2-4 hours
P0	Lazy load images	High	Low	1 hour
P0	Add image dimensions	High	Low	1 hour
P0	Minify assets	High	Low	1 hour
P1	Code splitting	High	Medium	4-8 hours
P1	Critical CSS	High	Medium	4-6 hours
P1	Font optimization	Medium	Low	2-3 hours
P1	Resource hints	Medium	Low	2 hours
P2	Service Worker	Medium	High	8-16 hours
P2	Third-party optimization	Medium	Medium	4-8 hours

1️⃣ COMPRESSION SETUP

1.1 Enable Brotli Compression

Nginx Configuration

# /etc/nginx/nginx.conf

http {
    # Enable Brotli
    brotli on;
    brotli_comp_level 6;  # 0-11, 6 is recommended for balance
    brotli_types 
        text/plain
        text/css
        text/xml
        text/javascript
        application/json
        application/javascript
        application/x-javascript
        application/xml
        application/xml+rss
        application/xhtml+xml
        application/rss+xml
        application/atom+xml
        image/svg+xml
        font/opentype
        font/ttf
        font/eot
        font/otf;
    
    # Fallback to gzip
    gzip on;
    gzip_comp_level 6;
    gzip_vary on;
    gzip_proxied any;
    gzip_types text/plain text/css text/xml text/javascript 
               application/json application/javascript application/xml+rss 
               application/atom+xml image/svg+xml;
}

Apache Configuration

# .htaccess or httpd.conf

<IfModule mod_brotli.c>
    AddOutputFilterByType BROTLI_COMPRESS text/html text/plain text/xml text/css text/javascript
    AddOutputFilterByType BROTLI_COMPRESS application/javascript application/json application/xml
    AddOutputFilterByType BROTLI_COMPRESS image/svg+xml font/opentype font/ttf font/eot font/otf
    BrotliCompressionQuality 6
</IfModule>

<IfModule mod_deflate.c>
    AddOutputFilterByType DEFLATE text/html text/plain text/xml text/css text/javascript
    AddOutputFilterByType DEFLATE application/javascript application/json application/xml
    AddOutputFilterByType DEFLATE image/svg+xml
</IfModule>

Cloudflare (Automatic)

1. Navigate to Speed > Optimization
2. Enable "Brotli" compression
3. Enable "Auto Minify" for HTML, CSS, JS

1.2 Verify Compression

# Check if Brotli is enabled
curl -H "Accept-Encoding: br" -I https://your-site.com

# Check if gzip is enabled
curl -H "Accept-Encoding: gzip" -I https://your-site.com

# Check compression ratio
curl -H "Accept-Encoding: gzip" https://your-site.com | wc -c
curl https://your-site.com | wc -c

2️⃣ IMAGE OPTIMIZATION

2.1 Convert to Modern Formats

Using Sharp (Node.js)

// build-scripts/optimize-images.js

const sharp = require('sharp');
const fs = require('fs');
const path = require('path');

async function convertToWebP(inputPath, outputPath) {
  await sharp(inputPath)
    .webp({ quality: 85, effort: 6 })
    .toFile(outputPath);
}

async function convertToAVIF(inputPath, outputPath) {
  await sharp(inputPath)
    .avif({ quality: 80, effort: 6 })
    .toFile(outputPath);
}

// Process all images in directory
async function processImages(directory) {
  const files = fs.readdirSync(directory);
  
  for (const file of files) {
    if (/\.(jpg|jpeg|png)$/i.test(file)) {
      const inputPath = path.join(directory, file);
      const baseName = path.parse(file).name;
      
      // Generate WebP
      await convertToWebP(
        inputPath, 
        path.join(directory, `${baseName}.webp`)
      );
      
      // Generate AVIF
      await convertToAVIF(
        inputPath, 
        path.join(directory, `${baseName}.avif`)
      );
      
      console.log(`Processed: ${file}`);
    }
  }
}

processImages('./public/images');

Using ImageMagick (CLI)

# Convert to WebP
find ./images -name "*.jpg" -o -name "*.png" | while read img; do
  cwebp -q 85 "$img" -o "${img%.*}.webp"
done

# Convert to AVIF
find ./images -name "*.jpg" -o -name "*.png" | while read img; do
  avifenc --min 0 --max 63 -a end-usage=q -a cq-level=23 "$img" "${img%.*}.avif"
done

2.2 Implement Responsive Images

HTML with Multiple Formats

<picture>
  <source 
    type="image/avif"
    srcset="
      /images/hero-400.avif 400w,
      /images/hero-800.avif 800w,
      /images/hero-1200.avif 1200w,
      /images/hero-1600.avif 1600w"
    sizes="(max-width: 600px) 100vw, 
           (max-width: 1200px) 50vw, 
           800px">
  <source 
    type="image/webp"
    srcset="
      /images/hero-400.webp 400w,
      /images/hero-800.webp 800w,
      /images/hero-1200.webp 1200w,
      /images/hero-1600.webp 1600w"
    sizes="(max-width: 600px) 100vw, 
           (max-width: 1200px) 50vw, 
           800px">
  <img 
    src="/images/hero-800.jpg"
    srcset="
      /images/hero-400.jpg 400w,
      /images/hero-800.jpg 800w,
      /images/hero-1200.jpg 1200w"
    sizes="(max-width: 600px) 100vw, 
           (max-width: 1200px) 50vw, 
           800px"
    alt="Hero image description"
    width="1200"
    height="675"
    loading="lazy"
    decoding="async">
</picture>

2.3 Automated Image Optimization Build Script

package.json

{
  "scripts": {
    "optimize:images": "node scripts/optimize-images.js",
    "prebuild": "npm run optimize:images"
  },
  "devDependencies": {
    "sharp": "^0.32.0",
    "imagemin": "^8.0.1",
    "imagemin-mozjpeg": "^10.0.0",
    "imagemin-pngquant": "^9.0.2",
    "imagemin-webp": "^7.0.0"
  }
}

2.4 Next.js Image Component

import Image from 'next/image';

export default function OptimizedImage() {
  return (
    <Image
      src="/images/hero.jpg"
      alt="Hero image"
      width={1200}
      height={675}
      priority={true}  // For LCP image
      quality={85}
      placeholder="blur"
      blurDataURL="data:image/jpeg;base64,..."
    />
  );
}

3️⃣ LAZY LOADING IMPLEMENTATION

3.1 Native Lazy Loading

<!-- For images below the fold -->
<img 
  src="/images/content.jpg" 
  alt="Content image"
  width="800"
  height="600"
  loading="lazy"
  decoding="async">

<!-- For critical above-the-fold images -->
<img 
  src="/images/hero.jpg" 
  alt="Hero image"
  width="1200"
  height="675"
  loading="eager"
  fetchpriority="high">

<!-- For iframes -->
<iframe 
  src="https://www.youtube.com/embed/VIDEO_ID" 
  loading="lazy"
  title="Video title">
</iframe>

3.2 Intersection Observer (Custom Implementation)

// utils/lazy-load.js

class LazyLoader {
  constructor(options = {}) {
    this.options = {
      rootMargin: '50px',
      threshold: 0.01,
      ...options
    };
    
    this.observer = new IntersectionObserver(
      this.handleIntersection.bind(this),
      this.options
    );
  }

  observe(elements) {
    elements.forEach(element => {
      this.observer.observe(element);
    });
  }

  handleIntersection(entries) {
    entries.forEach(entry => {
      if (entry.isIntersecting) {
        this.loadElement(entry.target);
        this.observer.unobserve(entry.target);
      }
    });
  }

  loadElement(element) {
    if (element.tagName === 'IMG') {
      const src = element.dataset.src;
      const srcset = element.dataset.srcset;
      
      if (srcset) element.srcset = srcset;
      if (src) element.src = src;
    } else if (element.tagName === 'IFRAME') {
      element.src = element.dataset.src;
    }
    
    element.classList.remove('lazy');
    element.classList.add('loaded');
  }
}

// Initialize
const lazyLoader = new LazyLoader();
const lazyImages = document.querySelectorAll('img.lazy, iframe.lazy');
lazyLoader.observe(lazyImages);

3.3 React Lazy Loading Component

// components/LazyImage.jsx

import { useState, useEffect, useRef } from 'react';

export default function LazyImage({ src, alt, width, height, className }) {
  const [isLoaded, setIsLoaded] = useState(false);
  const [isInView, setIsInView] = useState(false);
  const imgRef = useRef(null);

  useEffect(() => {
    const observer = new IntersectionObserver(
      ([entry]) => {
        if (entry.isIntersecting) {
          setIsInView(true);
          observer.disconnect();
        }
      },
      { rootMargin: '50px' }
    );

    if (imgRef.current) {
      observer.observe(imgRef.current);
    }

    return () => observer.disconnect();
  }, []);

  return (
    <div 
      ref={imgRef}
      style={{ 
        width, 
        height, 
        position: 'relative',
        backgroundColor: '#f0f0f0'
      }}
      className={className}
    >
      {isInView && (
        <img
          src={src}
          alt={alt}
          width={width}
          height={height}
          onLoad={() => setIsLoaded(true)}
          style={{
            opacity: isLoaded ? 1 : 0,
            transition: 'opacity 0.3s'
          }}
        />
      )}
    </div>
  );
}

4️⃣ CRITICAL CSS EXTRACTION

4.1 Using Critical Package

// scripts/extract-critical.js

const critical = require('critical');
const fs = require('fs');
const path = require('path');

async function extractCritical() {
  const pages = [
    { url: 'index.html', output: 'index-critical.html' },
    { url: 'about.html', output: 'about-critical.html' },
    { url: 'product.html', output: 'product-critical.html' }
  ];

  for (const page of pages) {
    try {
      const { html } = await critical.generate({
        src: page.url,
        target: {
          html: page.output,
          css: `${path.parse(page.output).name}-critical.css`
        },
        width: 1300,
        height: 900,
        dimensions: [
          { width: 375, height: 667 },   // Mobile
          { width: 768, height: 1024 },  // Tablet
          { width: 1300, height: 900 }   // Desktop
        ],
        inline: true,
        extract: true,
        penthouse: {
          timeout: 60000
        }
      });

      console.log(`Generated critical CSS for ${page.url}`);
    } catch (err) {
      console.error(`Error processing ${page.url}:`, err);
    }
  }
}

extractCritical();

4.2 Manual Critical CSS Approach

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Page Title</title>
  
  <!-- Inline Critical CSS -->
  <style>
    /* Critical styles for above-the-fold content */
    body { margin: 0; font-family: sans-serif; }
    .header { background: #000; color: #fff; padding: 1rem; }
    .hero { height: 100vh; background: url('/hero-thumb.jpg'); }
    /* ... more critical styles ... */
  </style>
  
  <!-- Preload full stylesheet -->
  <link rel="preload" href="/styles/main.css" as="style" onload="this.onload=null;this.rel='stylesheet'">
  <noscript><link rel="stylesheet" href="/styles/main.css"></noscript>
  
  <!-- Async CSS loading script -->
  <script>
    !function(e){"use strict";var t=function(t,n,r,o){var i,a=e.document,d=a.createElement("link");if(n)i=n;else{var f=(a.body||a.getElementsByTagName("head")[0]).childNodes;i=f[f.length-1]}var l=a.styleSheets;if(o)for(var s in o)o.hasOwnProperty(s)&&d.setAttribute(s,o[s]);d.rel="stylesheet",d.href=t,d.media="only x",function e(t){if(a.body)return t();setTimeout(function(){e(t)})}(function(){i.parentNode.insertBefore(d,n?i:i.nextSibling)});var u=function(e){for(var t=d.href,n=l.length;n--;)if(l[n].href===t)return e();setTimeout(function(){u(e)})};function c(){d.addEventListener&&d.removeEventListener("load",c),d.media=r||"all"}return d.addEventListener&&d.addEventListener("load",c),(d.onloadcssdefined=u)(c),d};"undefined"!=typeof exports?exports.loadCSS=t:e.loadCSS=t}("undefined"!=typeof global?global:this);
  </script>
</head>
<body>
  <!-- Page content -->
</body>
</html>

4.3 Webpack Critical CSS Plugin

// webpack.config.js

const HtmlWebpackPlugin = require('html-webpack-plugin');
const HtmlCriticalWebpackPlugin = require('html-critical-webpack-plugin');

module.exports = {
  // ... other config
  plugins: [
    new HtmlWebpackPlugin({
      template: 'src/index.html'
    }),
    new HtmlCriticalWebpackPlugin({
      base: path.resolve(__dirname, 'dist'),
      src: 'index.html',
      dest: 'index.html',
      inline: true,
      minify: true,
      extract: true,
      width: 1300,
      height: 900,
      penthouse: {
        blockJSRequests: false,
      }
    })
  ]
};

5️⃣ JAVASCRIPT OPTIMIZATION

5.1 Code Splitting (Webpack)

// webpack.config.js

module.exports = {
  entry: {
    main: './src/index.js',
  },
  output: {
    filename: '[name].[contenthash].js',
    chunkFilename: '[name].[contenthash].chunk.js',
    path: path.resolve(__dirname, 'dist'),
  },
  optimization: {
    splitChunks: {
      chunks: 'all',
      maxInitialRequests: Infinity,
      minSize: 20000,
      cacheGroups: {
        vendor: {
          test: /[\\/]node_modules[\\/]/,
          name(module) {
            // Get package name
            const packageName = module.context.match(
              /[\\/]node_modules[\\/](.*?)([\\/]|$)/
            )[1];
            return `npm.${packageName.replace('@', '')}`;
          },
          priority: 10,
        },
        common: {
          minChunks: 2,
          priority: 5,
          reuseExistingChunk: true,
        },
      },
    },
    runtimeChunk: 'single',
  },
};

5.2 Dynamic Imports

// React component with lazy loading

import React, { lazy, Suspense } from 'react';

// Lazy load heavy components
const HeavyChart = lazy(() => import('./components/HeavyChart'));
const VideoPlayer = lazy(() => import('./components/VideoPlayer'));
const ImageGallery = lazy(() => import('./components/ImageGallery'));

function App() {
  return (
    <div>
      <Header />
      
      <Suspense fallback={<LoadingSpinner />}>
        <HeavyChart data={chartData} />
      </Suspense>
      
      <Suspense fallback={<div>Loading video...</div>}>
        <VideoPlayer src="/video.mp4" />
      </Suspense>
      
      <Suspense fallback={<div>Loading gallery...</div>}>
        <ImageGallery images={images} />
      </Suspense>
    </div>
  );
}

// Route-based code splitting
const Home = lazy(() => import('./pages/Home'));
const About = lazy(() => import('./pages/About'));
const Products = lazy(() => import('./pages/Products'));

function Routes() {
  return (
    <Suspense fallback={<PageLoader />}>
      <Switch>
        <Route exact path="/" component={Home} />
        <Route path="/about" component={About} />
        <Route path="/products" component={Products} />
      </Switch>
    </Suspense>
  );
}

5.3 Script Loading Strategy

<!-- Critical scripts - defer -->
<script src="/js/critical.js" defer></script>

<!-- Non-critical scripts - async -->
<script src="/js/analytics.js" async></script>

<!-- Third-party scripts - async with loading strategy -->
<script>
  // Load third-party script after page load
  window.addEventListener('load', () => {
    const script = document.createElement('script');
    script.src = 'https://example.com/widget.js';
    script.async = true;
    document.body.appendChild(script);
  });
</script>

<!-- Or use requestIdleCallback -->
<script>
  if ('requestIdleCallback' in window) {
    requestIdleCallback(() => {
      const script = document.createElement('script');
      script.src = 'https://example.com/widget.js';
      document.body.appendChild(script);
    });
  } else {
    // Fallback for browsers without requestIdleCallback
    setTimeout(() => {
      const script = document.createElement('script');
      script.src = 'https://example.com/widget.js';
      document.body.appendChild(script);
    }, 1000);
  }
</script>

5.4 Tree Shaking Configuration

// package.json

{
  "sideEffects": [
    "*.css",
    "*.scss",
    "./src/polyfills.js"
  ]
}

// webpack.config.js
module.exports = {
  mode: 'production',
  optimization: {
    usedExports: true,
    minimize: true,
    minimizer: [
      new TerserPlugin({
        terserOptions: {
          compress: {
            drop_console: true,
            pure_funcs: ['console.log', 'console.info', 'console.debug']
          },
          mangle: true,
        },
      }),
    ],
  },
};

// Import only what you need
import { debounce, throttle } from 'lodash-es';  // ✅ Good
// import _ from 'lodash';  // ❌ Imports entire library

6️⃣ FONT OPTIMIZATION

6.1 Font Loading Strategy

<!-- Preload critical fonts -->
<link 
  rel="preload" 
  href="/fonts/primary-font-regular.woff2" 
  as="font" 
  type="font/woff2" 
  crossorigin>

<link 
  rel="preload" 
  href="/fonts/primary-font-bold.woff2" 
  as="font" 
  type="font/woff2" 
  crossorigin>

<style>
  @font-face {
    font-family: 'PrimaryFont';
    src: url('/fonts/primary-font-regular.woff2') format('woff2');
    font-weight: 400;
    font-style: normal;
    font-display: swap;  /* or 'optional' for better CLS */
  }

  @font-face {
    font-family: 'PrimaryFont';
    src: url('/fonts/primary-font-bold.woff2') format('woff2');
    font-weight: 700;
    font-style: normal;
    font-display: swap;
  }
</style>

6.2 Font Subsetting

# Using pyftsubset (part of fonttools)
pip install fonttools brotli

# Subset to include only Latin characters
pyftsubset font.ttf \
  --unicodes="U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+2000-206F, U+2074, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD" \
  --flavor=woff2 \
  --output-file=font-subset.woff2

# Or use glyphhanger
npm install -g glyphhanger

# Generate subset based on actual usage on your site
glyphhanger https://your-site.com --subset=font.ttf --formats=woff2

6.3 Variable Fonts

@font-face {
  font-family: 'InterVariable';
  src: url('/fonts/Inter-Variable.woff2') format('woff2');
  font-weight: 100 900;  /* Variable weight range */
  font-display: swap;
}

body {
  font-family: 'InterVariable', sans-serif;
  font-weight: 400;
}

h1 {
  font-weight: 700;
  /* Same font file, different weight */
}

6.4 Font Loading Detection

// Detect when fonts are loaded
if ('fonts' in document) {
  document.fonts.ready.then(() => {
    document.body.classList.add('fonts-loaded');
  });
}

// Or use Font Face Observer library
const FontFaceObserver = require('fontfaceobserver');

const font = new FontFaceObserver('PrimaryFont');

font.load().then(() => {
  document.documentElement.classList.add('fonts-loaded');
}).catch(() => {
  // Font failed to load
  console.warn('Font loading failed');
});

7️⃣ CACHING CONFIGURATION

7.1 Cache-Control Headers (Nginx)

# /etc/nginx/sites-available/your-site

server {
    listen 443 ssl http2;
    server_name your-site.com;

    # HTML - no cache
    location ~* \.html$ {
        add_header Cache-Control "no-cache, no-store, must-revalidate";
        add_header Pragma "no-cache";
        add_header Expires "0";
    }

    # CSS and JavaScript - versioned files (immutable)
    location ~* \.(css|js)$ {
        add_header Cache-Control "public, max-age=31536000, immutable";
        access_log off;
    }

    # Images - long cache
    location ~* \.(jpg|jpeg|png|gif|webp|avif|svg|ico)$ {
        add_header Cache-Control "public, max-age=31536000, immutable";
        access_log off;
    }

    # Fonts - long cache with crossorigin
    location ~* \.(woff|woff2|ttf|eot)$ {
        add_header Cache-Control "public, max-age=31536000, immutable";
        add_header Access-Control-Allow-Origin "*";
        access_log off;
    }

    # API responses - short cache
    location /api/ {
        add_header Cache-Control "private, max-age=300, stale-while-revalidate=60";
    }
}

7.2 Apache .htaccess

# .htaccess

<IfModule mod_expires.c>
    ExpiresActive On
    
    # HTML
    ExpiresByType text/html "access plus 0 seconds"
    
    # CSS and JavaScript
    ExpiresByType text/css "access plus 1 year"
    ExpiresByType application/javascript "access plus 1 year"
    
    # Images
    ExpiresByType image/jpeg "access plus 1 year"
    ExpiresByType image/png "access plus 1 year"
    ExpiresByType image/webp "access plus 1 year"
    ExpiresByType image/svg+xml "access plus 1 year"
    
    # Fonts
    ExpiresByType font/woff2 "access plus 1 year"
    ExpiresByType font/woff "access plus 1 year"
</IfModule>

<IfModule mod_headers.c>
    # Immutable cache for versioned files
    <FilesMatch "\.(css|js|jpg|jpeg|png|webp|woff2|woff)$">
        Header set Cache-Control "public, max-age=31536000, immutable"
    </FilesMatch>
    
    # No cache for HTML
    <FilesMatch "\.html$">
        Header set Cache-Control "no-cache, no-store, must-revalidate"
    </FilesMatch>
</IfModule>

7.3 Service Worker Caching

// service-worker.js

const CACHE_VERSION = 'v1';
const CACHE_STATIC = `static-${CACHE_VERSION}`;
const CACHE_DYNAMIC = `dynamic-${CACHE_VERSION}`;

const STATIC_ASSETS = [
  '/',
  '/styles/main.css',
  '/js/app.js',
  '/fonts/primary-font.woff2',
  '/images/logo.svg'
];

// Install event - cache static assets
self.addEventListener('install', event => {
  event.waitUntil(
    caches.open(CACHE_STATIC)
      .then(cache => cache.addAll(STATIC_ASSETS))
      .then(() => self.skipWaiting())
  );
});

// Activate event - clean old caches
self.addEventListener('activate', event => {
  event.waitUntil(
    caches.keys()
      .then(keys => {
        return Promise.all(
          keys
            .filter(key => key !== CACHE_STATIC && key !== CACHE_DYNAMIC)
            .map(key => caches.delete(key))
        );
      })
      .then(() => self.clients.claim())
  );
});

// Fetch event - serve from cache, fallback to network
self.addEventListener('fetch', event => {
  const { request } = event;
  const url = new URL(request.url);

  // Cache-first strategy for static assets
  if (STATIC_ASSETS.includes(url.pathname)) {
    event.respondWith(
      caches.match(request)
        .then(response => response || fetch(request))
    );
    return;
  }

  // Network-first strategy for API calls
  if (url.pathname.startsWith('/api/')) {
    event.respondWith(
      fetch(request)
        .then(response => {
          // Clone and cache successful responses
          if (response.ok) {
            const responseClone = response.clone();
            caches.open(CACHE_DYNAMIC)
              .then(cache => cache.put(request, responseClone));
          }
          return response;
        })
        .catch(() => caches.match(request))
    );
    return;
  }

  // Stale-while-revalidate for everything else
  event.respondWith(
    caches.match(request)
      .then(cachedResponse => {
        const fetchPromise = fetch(request)
          .then(networkResponse => {
            if (networkResponse.ok) {
              const responseClone = networkResponse.clone();
              caches.open(CACHE_DYNAMIC)
                .then(cache => cache.put(request, responseClone));
            }
            return networkResponse;
          });
        return cachedResponse || fetchPromise;
      })
  );
});

8️⃣ RESOURCE HINTS

8.1 Preconnect and DNS Prefetch

<!-- Preconnect to critical third-party origins -->
<link rel="preconnect" href="https://fonts.googleapis.com">
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
<link rel="preconnect" href="https://cdn.example.com">

<!-- DNS prefetch for less critical third-parties -->
<link rel="dns-prefetch" href="https://analytics.google.com">
<link rel="dns-prefetch" href="https://www.googletagmanager.com">

8.2 Preload Critical Resources

<!-- Preload LCP image -->
<link 
  rel="preload" 
  as="image" 
  href="/images/hero.webp"
  type="image/webp"
  imagesrcset="/images/hero-400.webp 400w, /images/hero-800.webp 800w, /images/hero-1200.webp 1200w"
  imagesizes="100vw">

<!-- Preload critical CSS -->
<link 
  rel="preload" 
  as="style" 
  href="/styles/critical.css">

<!-- Preload critical JavaScript -->
<link 
  rel="preload" 
  as="script" 
  href="/js/critical.js">

<!-- Preload fonts -->
<link 
  rel="preload" 
  as="font" 
  type="font/woff2" 
  href="/fonts/primary.woff2" 
  crossorigin>

8.3 Prefetch for Likely Navigation

<!-- Prefetch next likely page -->
<link rel="prefetch" href="/products.html">
<link rel="prefetch" href="/about.html">

<!-- Prefetch resources for next page -->
<link rel="prefetch" as="image" href="/images/products-hero.webp">
<link rel="prefetch" as="script" href="/js/products.js">

8.4 Dynamic Resource Hints

// Prefetch on hover
document.querySelectorAll('a[href]').forEach(link => {
  link.addEventListener('mouseenter', () => {
    const url = link.getAttribute('href');
    if (url && !url.startsWith('#')) {
      const prefetch = document.createElement('link');
      prefetch.rel = 'prefetch';
      prefetch.href = url;
      document.head.appendChild(prefetch);
    }
  }, { once: true });
});

// Prefetch on viewport entry
const observer = new IntersectionObserver(entries => {
  entries.forEach(entry => {
    if (entry.isIntersecting) {
      const link = entry.target;
      const url = link.getAttribute('href');
      if (url && !url.startsWith('#')) {
        const prefetch = document.createElement('link');
        prefetch.rel = 'prefetch';
        prefetch.href = url;
        document.head.appendChild(prefetch);
      }
      observer.unobserve(link);
    }
  });
});

document.querySelectorAll('a[href]').forEach(link => {
  observer.observe(link);
});

9️⃣ THIRD-PARTY OPTIMIZATION

9.1 YouTube Embed Facade

<!-- Lightweight facade instead of full embed -->
<div class="youtube-facade" data-video-id="dQw4w9WgXcQ">
  <img 
    src="https://img.youtube.com/vi/dQw4w9WgXcQ/hqdefault.jpg" 
    alt="Video thumbnail"
    loading="lazy">
  <button class="play-button" aria-label="Play video"></button>
</div>

<style>
.youtube-facade {
  position: relative;
  padding-bottom: 56.25%; /* 16:9 aspect ratio */
  cursor: pointer;
}
.youtube-facade img {
  position: absolute;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.play-button {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 68px;
  height: 48px;
  background: red;
  border: none;
  border-radius: 8px;
  cursor: pointer;
}
</style>

<script>
document.querySelectorAll('.youtube-facade').forEach(facade => {
  facade.addEventListener('click', function() {
    const videoId = this.dataset.videoId;
    const iframe = document.createElement('iframe');
    iframe.src = `https://www.youtube.com/embed/${videoId}?autoplay=1`;
    iframe.allow = 'accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture';
    iframe.allowFullscreen = true;
    iframe.style.cssText = 'position:absolute;top:0;left:0;width:100%;height:100%;border:0';
    this.innerHTML = '';
    this.appendChild(iframe);
  }, { once: true });
});
</script>

9.2 Async Analytics Loading

<!-- Google Analytics 4 - Async with minimal impact -->
<script>
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  gtag('js', new Date());
  gtag('config', 'G-XXXXXXXXXX');

  // Load GA script after page load
  window.addEventListener('load', () => {
    const script = document.createElement('script');
    script.src = 'https://www.googletagmanager.com/gtag/js?id=G-XXXXXXXXXX';
    script.async = true;
    document.head.appendChild(script);
  });
</script>

<!-- Or use requestIdleCallback -->
<script>
  if ('requestIdleCallback' in window) {
    requestIdleCallback(() => {
      (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
      new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
      j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
      'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
      })(window,document,'script','dataLayer','GTM-XXXXXXX');
    });
  }
</script>

9.3 Facebook Pixel Optimization

<script>
  // Minimal Facebook Pixel implementation
  !function(f,b,e,v,n,t,s)
  {if(f.fbq)return;n=f.fbq=function(){n.callMethod?
  n.callMethod.apply(n,arguments):n.queue.push(arguments)};
  if(!f._fbq)f._fbq=n;n.push=n;n.loaded=!0;n.version='2.0';
  n.queue=[];
  
  // Load after page load
  window.addEventListener('load', () => {
    t=b.createElement(e);t.async=!0;
    t.src=v;s=b.getElementsByTagName(e)[0];
    s.parentNode.insertBefore(t,s);
  });
  }(window, document,'script','https://connect.facebook.net/en_US/fbevents.js');
  
  fbq('init', 'YOUR_PIXEL_ID');
  fbq('track', 'PageView');
</script>

🔟 WEB VITALS MONITORING

10.1 Web Vitals Library Implementation

// analytics.js

import { onCLS, onFCP, onFID, onLCP, onTTFB, onINP } from 'web-vitals';

function sendToAnalytics(metric) {
  // Send to Google Analytics
  if (typeof gtag !== 'undefined') {
    gtag('event', metric.name, {
      event_category: 'Web Vitals',
      event_label: metric.id,
      value: Math.round(metric.name === 'CLS' ? metric.value * 1000 : metric.value),
      non_interaction: true,
    });
  }

  // Send to custom analytics endpoint
  const data = {
    metric: metric.name,
    value: metric.value,
    id: metric.id,
    delta: metric.delta,
    rating: metric.rating,
    url: window.location.href,
    userAgent: navigator.userAgent,
    connectionType: navigator.connection?.effectiveType
  };

  if (navigator.sendBeacon) {
    navigator.sendBeacon('/api/vitals', JSON.stringify(data));
  } else {
    fetch('/api/vitals', {
      method: 'POST',
      body: JSON.stringify(data),
      headers: { 'Content-Type': 'application/json' },
      keepalive: true
    });
  }
}

// Monitor all Core Web Vitals
onCLS(sendToAnalytics);
onFCP(sendToAnalytics);
onINP(sendToAnalytics);
onLCP(sendToAnalytics);
onTTFB(sendToAnalytics);

10.2 Custom Performance Monitoring

// performance-monitor.js

class PerformanceMonitor {
  constructor() {
    this.metrics = {};
    this.init();
  }

  init() {
    if ('PerformanceObserver' in window) {
      // Observe LCP
      this.observeLCP();
      // Observe FCP
      this.observeFCP();
      // Observe CLS
      this.observeCLS();
      // Observe long tasks
      this.observeLongTasks();
    }

    // Navigation Timing
    window.addEventListener('load', () => {
      this.captureNavigationTiming();
    });
  }

  observeLCP() {
    const observer = new PerformanceObserver((list) => {
      const entries = list.getEntries();
      const lastEntry = entries[entries.length - 1];
      this.metrics.lcp = lastEntry.renderTime || lastEntry.loadTime;
      this.report('LCP', this.metrics.lcp);
    });
    observer.observe({ entryTypes: ['largest-contentful-paint'] });
  }

  observeFCP() {
    const observer = new PerformanceObserver((list) => {
      const entries = list.getEntries();
      entries.forEach((entry) => {
        if (entry.name === 'first-contentful-paint') {
          this.metrics.fcp = entry.startTime;
          this.report('FCP', this.metrics.fcp);
        }
      });
    });
    observer.observe({ entryTypes: ['paint'] });
  }

  observeCLS() {
    let clsValue = 0;
    const observer = new PerformanceObserver((list) => {
      for (const entry of list.getEntries()) {
        if (!entry.hadRecentInput) {
          clsValue += entry.value;
          this.metrics.cls = clsValue;
        }
      }
      this.report('CLS', this.metrics.cls);
    });
    observer.observe({ entryTypes: ['layout-shift'] });
  }

  observeLongTasks() {
    const observer = new PerformanceObserver((list) => {
      const entries = list.getEntries();
      this.metrics.longTasks = entries.length;
      this.metrics.totalBlockingTime = entries.reduce(
        (acc, entry) => acc + Math.max(0, entry.duration - 50),
        0
      );
      this.report('Long Tasks', this.metrics.longTasks);
    });
    observer.observe({ entryTypes: ['longtask'] });
  }

  captureNavigationTiming() {
    const timing = performance.getEntriesByType('navigation')[0];
    if (timing) {
      this.metrics.ttfb = timing.responseStart - timing.requestStart;
      this.metrics.domLoad = timing.domContentLoadedEventEnd - timing.fetchStart;
      this.metrics.windowLoad = timing.loadEventEnd - timing.fetchStart;
      
      this.report('Navigation Timing', {
        ttfb: this.metrics.ttfb,
        domLoad: this.metrics.domLoad,
        windowLoad: this.metrics.windowLoad
      });
    }
  }

  report(metricName, value) {
    console.log(`${metricName}:`, value);
    
    // Send to analytics
    if (navigator.sendBeacon) {
      navigator.sendBeacon('/api/metrics', JSON.stringify({
        metric: metricName,
        value: value,
        url: window.location.href,
        timestamp: Date.now()
      }));
    }
  }

  getMetrics() {
    return this.metrics;
  }
}

// Initialize
const monitor = new PerformanceMonitor();
window.performanceMonitor = monitor;

1️⃣1️⃣ BUILD PROCESS OPTIMIZATION

11.1 Webpack Production Config

// webpack.prod.js

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const CssMinimizerPlugin = require('css-minimizer-webpack-plugin');
const TerserPlugin = require('terser-webpack-plugin');
const CompressionPlugin = require('compression-webpack-plugin');
const { BundleAnalyzerPlugin } = require('webpack-bundle-analyzer');

module.exports = {
  mode: 'production',
  entry: './src/index.js',
  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: 'js/[name].[contenthash:8].js',
    chunkFilename: 'js/[name].[contenthash:8].chunk.js',
    publicPath: '/',
    clean: true,
  },
  
  optimization: {
    minimize: true,
    minimizer: [
      new TerserPlugin({
        terserOptions: {
          parse: { ecma: 8 },
          compress: {
            ecma: 5,
            warnings: false,
            comparisons: false,
            inline: 2,
            drop_console: true,
            pure_funcs: ['console.log', 'console.info'],
          },
          mangle: { safari10: true },
          output: {
            ecma: 5,
            comments: false,
            ascii_only: true,
          },
        },
        parallel: true,
      }),
      new CssMinimizerPlugin(),
    ],
    
    splitChunks: {
      chunks: 'all',
      maxInitialRequests: 25,
      minSize: 20000,
      cacheGroups: {
        defaultVendors: {
          test: /[\\/]node_modules[\\/]/,
          priority: -10,
          reuseExistingChunk: true,
          name(module) {
            const packageName = module.context.match(
              /[\\/]node_modules[\\/](.*?)([\\/]|$)/
            )[1];
            return `npm.${packageName.replace('@', '')}`;
          },
        },
        default: {
          minChunks: 2,
          priority: -20,
          reuseExistingChunk: true,
        },
      },
    },
    
    runtimeChunk: 'single',
    moduleIds: 'deterministic',
  },
  
  plugins: [
    new HtmlWebpackPlugin({
      template: './src/index.html',
      minify: {
        removeComments: true,
        collapseWhitespace: true,
        removeRedundantAttributes: true,
        useShortDoctype: true,
        removeEmptyAttributes: true,
        removeStyleLinkTypeAttributes: true,
        keepClosingSlash: true,
        minifyJS: true,
        minifyCSS: true,
        minifyURLs: true,
      },
    }),
    
    new MiniCssExtractPlugin({
      filename: 'css/[name].[contenthash:8].css',
      chunkFilename: 'css/[name].[contenthash:8].chunk.css',
    }),
    
    new CompressionPlugin({
      filename: '[path][base].br',
      algorithm: 'brotliCompress',
      test: /\.(js|css|html|svg)$/,
      compressionOptions: { level: 11 },
      threshold: 10240,
      minRatio: 0.8,
    }),
    
    new CompressionPlugin({
      filename: '[path][base].gz',
      algorithm: 'gzip',
      test: /\.(js|css|html|svg)$/,
      threshold: 10240,
      minRatio: 0.8,
    }),
    
    // Analyze bundle only when needed
    process.env.ANALYZE && new BundleAnalyzerPlugin(),
  ].filter(Boolean),
  
  performance: {
    maxAssetSize: 250000,
    maxEntrypointSize: 250000,
    hints: 'warning',
  },
};

11.2 Next.js Configuration

// next.config.js

module.exports = {
  // Enable SWC minification
  swcMinify: true,
  
  // Compress output
  compress: true,
  
  // Image optimization
  images: {
    formats: ['image/avif', 'image/webp'],
    deviceSizes: [640, 750, 828, 1080, 1200, 1920, 2048, 3840],
    imageSizes: [16, 32, 48, 64, 96, 128, 256, 384],
    minimumCacheTTL: 31536000,
  },
  
  // Headers
  async headers() {
    return [
      {
        source: '/:all*(svg|jpg|jpeg|png|webp|avif|gif|ico)',
        headers: [
          {
            key: 'Cache-Control',
            value: 'public, max-age=31536000, immutable',
          },
        ],
      },
      {
        source: '/_next/static/:path*',
        headers: [
          {
            key: 'Cache-Control',
            value: 'public, max-age=31536000, immutable',
          },
        ],
      },
    ];
  },
  
  // Webpack customization
  webpack: (config, { dev, isServer }) => {
    // Production optimizations
    if (!dev && !isServer) {
      config.optimization.splitChunks = {
        chunks: 'all',
        cacheGroups: {
          default: false,
          vendors: false,
          commons: {
            name: 'commons',
            chunks: 'all',
            minChunks: 2,
          },
          react: {
            name: 'react',
            chunks: 'all',
            test: /[\\/]node_modules[\\/](react|react-dom|scheduler)[\\/]/,
          },
        },
      };
    }
    
    return config;
  },
};

1️⃣2️⃣ CONTINUOUS MONITORING

12.1 Lighthouse CI Configuration

# .lighthouserc.json

{
  "ci": {
    "collect": {
      "numberOfRuns": 3,
      "startServerCommand": "npm run serve",
      "url": [
        "http://localhost:3000",
        "http://localhost:3000/about",
        "http://localhost:3000/products"
      ],
      "settings": {
        "preset": "desktop",
        "throttling": {
          "rttMs": 40,
          "throughputKbps": 10240,
          "cpuSlowdownMultiplier": 1
        }
      }
    },
    "assert": {
      "assertions": {
        "categories:performance": ["error", {"minScore": 0.9}],
        "categories:accessibility": ["error", {"minScore": 0.9}],
        "categories:best-practices": ["error", {"minScore": 0.9}],
        "categories:seo": ["error", {"minScore": 0.9}],
        "first-contentful-paint": ["error", {"maxNumericValue": 1800}],
        "largest-contentful-paint": ["error", {"maxNumericValue": 2500}],
        "cumulative-layout-shift": ["error", {"maxNumericValue": 0.1}],
        "total-blocking-time": ["error", {"maxNumericValue": 200}]
      }
    },
    "upload": {
      "target": "temporary-public-storage"
    }
  }
}

12.2 GitHub Actions Workflow

# .github/workflows/performance.yml

name: Performance Check

on:
  pull_request:
    branches: [main]
  push:
    branches: [main]

jobs:
  lighthouse:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      
      - name: Setup Node
        uses: actions/setup-node@v3
        with:
          node-version: '18'
          cache: 'npm'
      
      - name: Install dependencies
        run: npm ci
      
      - name: Build
        run: npm run build
      
      - name: Run Lighthouse CI
        run: |
          npm install -g @lhci/[email protected]
          lhci autorun
        env:
          LHCI_GITHUB_APP_TOKEN: ${{ secrets.LHCI_GITHUB_APP_TOKEN }}
      
      - name: Upload results
        uses: actions/upload-artifact@v3
        with:
          name: lighthouse-results
          path: .lighthouseci

📊 PERFORMANCE BUDGET CONFIGURATION

package.json Budget Example

{
  "performance": {
    "budgets": [
      {
        "resourceSizes": [
          {
            "resourceType": "script",
            "budget": 300
          },
          {
            "resourceType": "stylesheet",
            "budget": 50
          },
          {
            "resourceType": "image",
            "budget": 500
          },
          {
            "resourceType": "font",
            "budget": 100
          },
          {
            "resourceType": "total",
            "budget": 1000
          }
        ],
        "resourceCounts": [
          {
            "resourceType": "script",
            "budget": 10
          },
          {
            "resourceType": "stylesheet",
            "budget": 3
          },
          {
            "resourceType": "third-party",
            "budget": 10
          }
        ]
      }
    ]
  }
}

🎉 IMPLEMENTATION CHECKLIST

Foundation

Core Optimizations

Advanced

Implement service worker
Add resource hints
Optimize third-party scripts
Set up performance monitoring

Polish & Monitor

Document Version: 1.0
Companion to: PageSpeed Universal Optimization Checklist
Last Updated: November 2025

PageSpeed Quick Reference Cheat Sheet

Most Impactful Optimizations for 90+ Scores

🎯 CORE WEB VITALS TARGETS

✅ LCP (Largest Contentful Paint)     ≤ 2.5s
✅ CLS (Cumulative Layout Shift)      ≤ 0.1
✅ INP (Interaction to Next Paint)    ≤ 200ms
✅ FCP (First Contentful Paint)       ≤ 1.8s
✅ TTFB (Time to First Byte)          ≤ 800ms

⚡ TOP 10 QUICK WINS

1. Enable Compression (30 min)

# Nginx
brotli on;
brotli_comp_level 6;
gzip on;
gzip_comp_level 6;

2. Add Image Dimensions (15 min)

<!-- ALWAYS include width and height -->
<img src="image.jpg" width="800" height="600" alt="Description">

3. Lazy Load Images (15 min)

<!-- Above fold -->
<img src="hero.jpg" loading="eager" fetchpriority="high">

<!-- Below fold -->
<img src="content.jpg" loading="lazy">

4. Use Modern Image Formats (1 hour)

<picture>
  <source srcset="image.avif" type="image/avif">
  <source srcset="image.webp" type="image/webp">
  <img src="image.jpg" alt="Fallback">
</picture>

5. Defer Non-Critical JS (15 min)

<script src="app.js" defer></script>
<script src="analytics.js" async></script>

6. Inline Critical CSS (2 hours)

<head>
  <style>/* Critical CSS here */</style>
  <link rel="preload" href="full.css" as="style" onload="this.rel='stylesheet'">
</head>

7. Optimize Fonts (1 hour)

<link rel="preload" href="font.woff2" as="font" type="font/woff2" crossorigin>
<style>
  @font-face {
    font-family: 'MyFont';
    src: url('font.woff2') format('woff2');
    font-display: swap;
  }
</style>

8. Set Cache Headers (30 min)

# Static assets - 1 year
location ~* \.(css|js|jpg|png|webp|woff2)$ {
    add_header Cache-Control "public, max-age=31536000, immutable";
}

# HTML - no cache
location ~* \.html$ {
    add_header Cache-Control "no-cache";
}

9. Preconnect to Third-Party Origins (10 min)

<link rel="preconnect" href="https://fonts.googleapis.com">
<link rel="preconnect" href="https://cdn.example.com">

10. Minify All Assets (30 min)

npm install -D terser cssnano html-minifier
# Add to build process

🖼️ IMAGE OPTIMIZATION COMMANDS

# Convert to WebP
cwebp -q 85 input.jpg -o output.webp

# Convert to AVIF  
avifenc --min 0 --max 63 input.jpg output.avif

# Optimize JPEG
jpegoptim --max=85 --strip-all *.jpg

# Optimize PNG
pngquant --quality=65-80 *.png

# Batch optimize with Sharp (Node.js)
npm install sharp
node -e "const sharp=require('sharp'); sharp('input.jpg').webp({quality:85}).toFile('output.webp');"

📱 RESPONSIVE IMAGES TEMPLATE

<picture>
  <!-- AVIF -->
  <source 
    type="image/avif"
    srcset="img-400.avif 400w, img-800.avif 800w, img-1200.avif 1200w"
    sizes="(max-width: 600px) 100vw, (max-width: 1200px) 50vw, 800px">
  
  <!-- WebP -->
  <source 
    type="image/webp"
    srcset="img-400.webp 400w, img-800.webp 800w, img-1200.webp 1200w"
    sizes="(max-width: 600px) 100vw, (max-width: 1200px) 50vw, 800px">
  
  <!-- Fallback -->
  <img 
    src="img-800.jpg"
    srcset="img-400.jpg 400w, img-800.jpg 800w, img-1200.jpg 1200w"
    sizes="(max-width: 600px) 100vw, (max-width: 1200px) 50vw, 800px"
    width="1200"
    height="675"
    alt="Description"
    loading="lazy">
</picture>

🎨 CRITICAL CSS EXTRACTION

# Install critical
npm install -g critical

# Extract critical CSS
critical index.html --base dist/ --inline > index-critical.html

# Or use in build script
npx critical index.html --base dist/ --inline

⚙️ WEBPACK PRODUCTION CONFIG (MINIMAL)

module.exports = {
  mode: 'production',
  optimization: {
    minimize: true,
    splitChunks: {
      chunks: 'all',
      cacheGroups: {
        vendor: {
          test: /[\\/]node_modules[\\/]/,
          name: 'vendors',
          priority: 10,
        },
      },
    },
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: '[name].[contenthash].css',
    }),
  ],
};

🔤 FONT OPTIMIZATION TEMPLATE

<!-- Preload critical fonts -->
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
<link rel="preload" href="/fonts/primary.woff2" as="font" type="font/woff2" crossorigin>

<style>
  @font-face {
    font-family: 'Primary';
    src: url('/fonts/primary.woff2') format('woff2');
    font-weight: 400;
    font-style: normal;
    font-display: swap; /* or 'optional' for better CLS */
  }
</style>

<!-- Self-hosted Google Fonts alternative -->
<!-- Use: https://google-webfonts-helper.herokuapp.com/ -->

🔗 RESOURCE HINTS PATTERN

<head>
  <!-- DNS Prefetch for third-parties -->
  <link rel="dns-prefetch" href="https://analytics.google.com">
  
  <!-- Preconnect for critical third-parties -->
  <link rel="preconnect" href="https://fonts.googleapis.com">
  <link rel="preconnect" href="https://cdn.example.com">
  
  <!-- Preload LCP image -->
  <link rel="preload" as="image" href="hero.webp">
  
  <!-- Preload critical CSS/JS -->
  <link rel="preload" as="style" href="critical.css">
  <link rel="preload" as="script" href="app.js">
  
  <!-- Preload critical font -->
  <link rel="preload" as="font" type="font/woff2" href="font.woff2" crossorigin>
  
  <!-- Prefetch next likely navigation -->
  <link rel="prefetch" href="/about.html">
</head>

📦 SERVICE WORKER (MINIMAL)

// sw.js
const CACHE = 'v1';
const ASSETS = ['/','/app.js','/style.css','/font.woff2'];

self.addEventListener('install', e => {
  e.waitUntil(caches.open(CACHE).then(cache => cache.addAll(ASSETS)));
});

self.addEventListener('fetch', e => {
  e.respondWith(
    caches.match(e.request).then(res => res || fetch(e.request))
  );
});

// Register in app
if ('serviceWorker' in navigator) {
  navigator.serviceWorker.register('/sw.js');
}

🎭 YOUTUBE EMBED FACADE

<div class="yt" data-id="VIDEO_ID" onclick="
  const iframe=document.createElement('iframe');
  iframe.src='https://www.youtube.com/embed/'+this.dataset.id+'?autoplay=1';
  iframe.allow='autoplay;encrypted-media';
  iframe.allowFullscreen=true;
  iframe.style='position:absolute;top:0;left:0;width:100%;height:100%';
  this.innerHTML='';
  this.appendChild(iframe);
" style="position:relative;padding-bottom:56.25%;background:url(https://img.youtube.com/vi/VIDEO_ID/hqdefault.jpg) center/cover;cursor:pointer">
  <button style="position:absolute;top:50%;left:50%;transform:translate(-50%,-50%);width:68px;height:48px;background:red;border:0;border-radius:8px"></button>
</div>

📊 WEB VITALS TRACKING

// Install: npm install web-vitals
import {onCLS, onFCP, onLCP, onTTFB, onINP} from 'web-vitals';

function sendToAnalytics({name, value, id}) {
  gtag('event', name, {
    event_category: 'Web Vitals',
    value: Math.round(name === 'CLS' ? value * 1000 : value),
    event_label: id,
    non_interaction: true,
  });
}

onCLS(sendToAnalytics);
onFCP(sendToAnalytics);
onLCP(sendToAnalytics);
onTTFB(sendToAnalytics);
onINP(sendToAnalytics);

🧪 TESTING COMMANDS

# Lighthouse CLI
npm install -g lighthouse
lighthouse https://your-site.com --view

# With specific settings
lighthouse https://your-site.com --preset=desktop --output=html --output-path=./report.html

# PageSpeed Insights API
curl "https://www.googleapis.com/pagespeedonline/v5/runPagespeed?url=https://your-site.com&strategy=mobile"

# Chrome DevTools Performance
# Open DevTools > Performance > Record > Stop > Analyze

# WebPageTest CLI
npm install -g webpagetest
webpagetest test https://your-site.com

📋 LCP OPTIMIZATION CHECKLIST

✅ Optimize server response (TTFB < 800ms)
✅ Eliminate render-blocking resources
✅ Use CDN for assets
✅ Preload LCP image
✅ Use appropriate image format (AVIF/WebP)
✅ Compress images (<200KB for hero)
✅ Set fetchpriority="high" on LCP image
✅ Avoid lazy loading LCP image
✅ Use HTTP/2 or HTTP/3
✅ Enable compression (Brotli)

📋 CLS OPTIMIZATION CHECKLIST

✅ Set width/height on all images
✅ Set dimensions for ads/embeds
✅ Reserve space for dynamic content
✅ Use font-display: swap/optional
✅ Preload critical fonts
✅ Avoid inserting content above viewport
✅ Use transform instead of layout properties
✅ Set aspect-ratio for responsive images
✅ Avoid animations of top/left/width/height
✅ Test with slow network (layout shifts often appear then)

📋 INP OPTIMIZATION CHECKLIST

✅ Break up long tasks (>50ms)
✅ Minimize JavaScript execution time
✅ Defer non-critical JavaScript
✅ Use code splitting
✅ Implement debounce/throttle for handlers
✅ Use passive event listeners
✅ Minimize third-party scripts
✅ Use web workers for heavy computation
✅ Reduce DOM complexity
✅ Optimize rendering work

🛠️ COMMON ISSUES & FIXES

Issue: High LCP

Fix:

Optimize hero image (WebP/AVIF, compression)
Preload LCP element
Reduce server response time
Eliminate render-blocking resources

Issue: High CLS

Fix:

Add explicit dimensions to images
Reserve space for ads/dynamic content
Preload fonts with font-display: swap

Issue: High INP

Fix:

Break up long JavaScript tasks
Reduce third-party script impact
Optimize event handlers
Use requestIdleCallback for non-urgent work

Issue: Render-Blocking Resources

Fix:

<!-- Inline critical CSS -->
<style>/* critical CSS */</style>

<!-- Defer JavaScript -->
<script src="app.js" defer></script>

<!-- Async load CSS -->
<link rel="preload" href="style.css" as="style" onload="this.rel='stylesheet'">

📊 PERFORMANCE BUDGET (REFERENCE)

JavaScript:       < 300KB (gzipped)
CSS:              < 50KB (gzipped)
Images (total):   < 500KB
Fonts:            < 100KB
Total page size:  < 1MB

LCP:              < 2.5s
FCP:              < 1.8s
CLS:              < 0.1
INP:              < 200ms
TTFB:             < 800ms

🎯 SEO QUICK CHECKS

<!-- Title (50-60 chars) -->
<title>Page Title | Site Name</title>

<!-- Meta Description (150-160 chars) -->
<meta name="description" content="Compelling description with keywords">

<!-- Viewport -->
<meta name="viewport" content="width=device-width, initial-scale=1">

<!-- Open Graph -->
<meta property="og:title" content="Title">
<meta property="og:description" content="Description">
<meta property="og:image" content="https://site.com/image.jpg">

<!-- Canonical -->
<link rel="canonical" href="https://site.com/page">

<!-- Schema.org (JSON-LD) -->
<script type="application/ld+json">
{
  "@context": "https://schema.org",
  "@type": "Article",
  "headline": "Article Title",
  "image": "image.jpg",
  "datePublished": "2025-01-01"
}
</script>

🔍 ACCESSIBILITY QUICK CHECKS

<!-- Images -->
<img src="image.jpg" alt="Descriptive text" width="800" height="600">

<!-- Links -->
<a href="/page">Descriptive link text (not "click here")</a>

<!-- Buttons -->
<button aria-label="Close dialog">×</button>

<!-- Headings (proper hierarchy) -->
<h1>Main Heading</h1>
<h2>Subheading</h2>

<!-- Form Labels -->
<label for="email">Email Address</label>
<input type="email" id="email" name="email">

<!-- Language -->
<html lang="en">

<!-- Focus visible -->
button:focus-visible {
  outline: 2px solid blue;
}

⚡ MOBILE-SPECIFIC OPTIMIZATIONS

<!-- Viewport -->
<meta name="viewport" content="width=device-width, initial-scale=1">

<!-- Touch Icons -->
<link rel="apple-touch-icon" href="icon-180.png">
<meta name="theme-color" content="#000000">

<!-- Disable zoom on input focus (use carefully) -->
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">

<!-- Optimize touch targets (48x48px minimum) -->
<style>
button, a {
  min-height: 48px;
  min-width: 48px;
}
</style>

🔄 CACHE HEADERS REFERENCE

# Nginx

# HTML - no cache
location ~* \.html$ {
    add_header Cache-Control "no-cache, no-store, must-revalidate";
}

# Versioned assets - 1 year cache
location ~* \.(css|js)$ {
    add_header Cache-Control "public, max-age=31536000, immutable";
}

# Images - 1 year cache
location ~* \.(jpg|jpeg|png|gif|webp|avif|svg|ico)$ {
    add_header Cache-Control "public, max-age=31536000, immutable";
}

# Fonts - 1 year cache + CORS
location ~* \.(woff|woff2|ttf|eot)$ {
    add_header Cache-Control "public, max-age=31536000, immutable";
    add_header Access-Control-Allow-Origin "*";
}

# API - short cache with revalidation
location /api/ {
    add_header Cache-Control "private, max-age=300, stale-while-revalidate=60";
}

📈 MONITORING SETUP

// Basic RUM setup
const observer = new PerformanceObserver((list) => {
  for (const entry of list.getEntries()) {
    // Send to analytics
    if (navigator.sendBeacon) {
      navigator.sendBeacon('/analytics', JSON.stringify({
        metric: entry.name,
        value: entry.value || entry.startTime,
        url: location.href
      }));
    }
  }
});

observer.observe({ entryTypes: ['paint', 'largest-contentful-paint', 'layout-shift'] });

🚀 QUICK DEPLOYMENT CHECKLIST

Before pushing to production:

📱 TEST DEVICES REFERENCE

Priority devices for testing:

iPhone 13/14 (iOS Safari)
Samsung Galaxy S21/S22 (Chrome Android)
iPad (Safari)
Desktop 1920×1080 (Chrome)
Desktop 1366×768 (Edge)

Network conditions to test:

Fast 3G (750 Kbps)
Slow 4G (4 Mbps)
WiFi (20+ Mbps)

🔗 ESSENTIAL TOOLS

Testing:
- PageSpeed Insights: https://pagespeed.web.dev/
- Lighthouse: https://developer.chrome.com/docs/lighthouse/
- WebPageTest: https://www.webpagetest.org/
- Chrome DevTools: Built into Chrome

Image Optimization:
- Squoosh: https://squoosh.app/
- ImageOptim: https://imageoptim.com/
- Sharp: https://sharp.pixelplumbing.com/

Monitoring:
- Google Search Console: https://search.google.com/search-console
- Chrome UX Report: https://developer.chrome.com/docs/crux/
- web-vitals library: https://github.com/GoogleChrome/web-vitals

Analysis:
- Webpack Bundle Analyzer: webpack plugin
- Bundlephobia: https://bundlephobia.com/

💡 PRO TIPS

Prioritize mobile first - Mobile performance is harder, optimize there first
Test on real devices - Emulators don't show real performance
Focus on Core Web Vitals - They have the most impact on UX and SEO
Set performance budgets - Prevent regressions with automated checks
Monitor continuously - Performance degrades over time, monitor it
Optimize images first - Usually the biggest wins for least effort
Lazy load everything below fold - Except critical content
Inline critical CSS only - Keep it under 14KB
Self-host fonts - Better caching, fewer connections
Test with slow networks - Many users have slow connections

Version: 1.0
Print this and keep it handy!
Last Updated: November 2025

[!NOTE] ### NOTE:

This is just provided as conceptual research, documentation, for informational-purposes only, etc., and has not been fully battle tested or vetted, however would appreciate hearing and learning about any implementations, and shared learnings. (Unless otherwise explicitly stated by the author.)

@TheDavidYoungblood

🤝 Let's Connect!

LinkedIn // GitHub // Medium // Twitter/X

You're invited to 'Buy Me A Coffee'...

A bit about David Youngblood...

David is a Partner, Father, Student, and Teacher, embodying the essence of a true polyoptic polymath and problem solver. As a Generative AI Prompt Engineer, Language Programmer, Context-Architect, and Artist, David seamlessly integrates technology, creativity, and strategic thinking to co-create systems of enablement and allowance that enhance experiences for everyone.

As a serial autodidact, David thrives on continuous learning and intellectual growth, constantly expanding his knowledge across diverse fields. His multifaceted career spans technology, sales, and the creative arts, showcasing his adaptability and relentless pursuit of excellence. At LouminAI Labs, David leads research initiatives that bridge the gap between advanced AI technologies and practical, impactful applications.

David's philosophy is rooted in thoughtful introspection and practical advice, guiding individuals to navigate the complexities of the digital age with self-awareness and intentionality. He passionately advocates for filtering out digital noise to focus on meaningful relationships, personal growth, and principled living. His work reflects a deep commitment to balance, resilience, and continuous improvement, inspiring others to live purposefully and authentically.

Personal Insights

David believes in the power of collaboration and principled responsibility in leveraging AI for the greater good. He challenges the status quo, inspired by the spirit of the "crazy ones" who push humanity forward. His commitment to meritocracy, excellence, and intelligence drives his approach to both personal and professional endeavors.

"Here’s to the crazy ones, the misfits, the rebels, the troublemakers, the round pegs in the square holes… the ones who see things differently; they’re not fond of rules, and they have no respect for the status quo… They push the human race forward, and while some may see them as the crazy ones, we see genius, because the people who are crazy enough to think that they can change the world, are the ones who do." — Apple, 1997

My Self-Q&A: A Work in Progress

Why I Exist? To experience life in every way, at every moment. To "BE".

What I Love to Do While Existing? Co-creating here, in our collective, combined, and interoperably shared experience.

How Do I Choose to Experience My Existence? I choose to do what I love. I love to co-create systems of enablement and allowance that help enhance anyone's experience.

Who Do I Love Creating for and With? Everyone of YOU! I seek to observe and appreciate the creativity and experiences made by, for, and from each of us.

When & Where Does All of This Take Place? Everywhere, in every moment, of every day. It's a very fulfilling place to be... I'm learning to be better about observing it as it occurs.

A Bit More...

I've learned a few overarching principles that now govern most of my day-to-day decision-making when it comes to how I choose to invest my time and who I choose to share it with:

Work/Life/Sleep (Health) Balance: Family first; does your schedule agree?
Love What You Do, and Do What You Love: If you have what you hold, what are YOU holding on to?
Response Over Reaction: Take pause and choose how to respond from the center, rather than simply react from habit, instinct, or emotion.
Progress Over Perfection: One of the greatest inhibitors of growth.
Inspired by "7 Habits of Highly Effective People": Integrating Covey’s principles into daily life.

Final Thoughts

David is dedicated to fostering meaningful connections and intentional living, leveraging his diverse skill set to make a positive impact in the world. Whether through his technical expertise, creative artistry, or philosophical insights, he strives to empower others to live their best lives by focusing on what truly matters.

— David Youngblood

thedavidyoungblood/DEV-DOCS_PageSpeed Optimization Master Index_MAIN-DOCUMENTATION.md

PageSpeed Optimization Master Index

Complete Guide Suite for 100%+ Performance Coverage

📚 DOCUMENT SUITE OVERVIEW

Document Hierarchy

📝 DOCUMENT MAP

📖 DOCUMENT 1: Universal Optimization Checklist

📖 DOCUMENT 2: Implementation Guide

📖 DOCUMENT 3: Quick Reference Cheat Sheet

🎯 HOW TO USE THIS SUITE

For New Projects

For Existing Projects

For Ongoing Maintenance

🎓 LEARNING PATH

Beginner Level

Intermediate Level

Advanced Level

🔄 WORKFLOW INTEGRATION

Development Workflow

Code Review Checklist

CI/CD Integration

📊 METRICS TRACKING

Key Performance Indicators

Measurement Frequency

🛠️ TOOLS REFERENCE

Essential Tools (From All Documents)

Tool Selection Guide

🎯 SUCCESS CRITERIA

Definition of Done

📋 COMMON SCENARIOS

Scenario 1: New E-commerce Site

Scenario 2: News/Blog Site

Scenario 3: Single Page Application (SPA)

Scenario 4: Marketing/Landing Page

🔍 TROUBLESHOOTING INDEX

Poor LCP Score

High CLS Score

High INP Score

Low Lighthouse Performance Score

📞 GETTING HELP

When to Use Each Document

Resource Escalation Path

🔄 DOCUMENT MAINTENANCE

Update Schedule

Version Control

📚 ADDITIONAL RESOURCES

Official Documentation

Learning Paths

Community

Tools & Services

✅ QUICK START CHECKLIST

🎓 CERTIFICATION PATH

Self-Assessment Levels

📈 SUCCESS METRICS

Individual Developer Metrics

Team Metrics

Business Metrics

🏆 BEST PRACTICES SUMMARY

🎯 FINAL RECOMMENDATIONS

For Maximum Impact

For Best Results

For Long-term Success

Universal PageSpeed Mobile & Desktop Optimization Checklist

Comprehensive ATOMIC-MECE Guide to 100%+ Performance Coverage

📊 PERFORMANCE THRESHOLDS REFERENCE

Core Web Vitals Targets (75th Percentile)

Additional Performance Metrics

Lighthouse Score Ranges

🎯 CATEGORY 1: CORE WEB VITALS OPTIMIZATION

1.1 Largest Contentful Paint (LCP) Optimization

1.1.1 Server Response Time (TTFB)

1.1.2 Resource Load Delay

1.1.3 Resource Load Time

1.1.4 Client-Side Rendering Delay

1.2 Cumulative Layout Shift (CLS) Optimization

1.2.1 Images Without Dimensions

1.2.2 Ads, Embeds, and Iframes

1.2.3 Dynamically Injected Content

1.2.4 Web Fonts Causing FOIT/FOUT

1.2.5 Animations