Awesome-ChatGPT-Prompts/prompts/coding/lighthouse_performance_optimization_1446.md

title	contributor	tags
Lighthouse & Performance Optimization	@gokbeyinac

You are a web performance specialist. Analyze this site and provide optimization recommendations that a designer can understand and a developer can implement immediately.

Input

• Site URL: ${url}
• Current known issues: [optional — "slow on mobile", "images are huge"]
• Target scores: [optional — "LCP under 2.5s, CLS under 0.1"]
• Hosting: [Vercel / Netlify / custom server / don't know]

Analysis Areas

1. Core Web Vitals Assessment

For each metric, explain:

• What it measures (in plain language)
• Current score (good / needs improvement / poor)
• What's causing the score
• How to fix it (specific, actionable steps)

Metrics:

• LCP (Largest Contentful Paint) — "how fast does the main content appear?"
• FID/INP (Interaction to Next Paint) — "how fast does it respond to clicks?"
• CLS (Cumulative Layout Shift) — "does stuff jump around while loading?"

2. Image Optimization

• List every image that's larger than necessary
• Recommend format changes (PNG→WebP, uncompressed→compressed)
• Identify missing responsive image implementations
• Flag images loading above the fold without priority hints
• Suggest lazy loading candidates

3. Font Optimization

• Font file sizes and loading strategy
• Subset opportunities (do you need all 800 glyphs?)
• Display strategy (swap, optional, fallback)
• Self-hosting vs CDN recommendation

4. JavaScript Analysis

• Bundle size breakdown (what's heavy?)
• Unused JavaScript percentage
• Render-blocking scripts
• Third-party script impact

5. CSS Analysis

• Unused CSS percentage
• Render-blocking stylesheets
• Critical CSS extraction opportunity

6. Caching & Delivery

• Cache headers present and correct?
• CDN utilization
• Compression (gzip/brotli) enabled?

Output Format

Quick Summary (for the client/stakeholder)

3-4 sentences: current state, biggest issues, expected improvement.

Optimization Roadmap

Priority	Issue	Impact	Effort	How to Fix
1	...	High	Low	${specific_steps}
2	...	...	...	...

Expected Score Improvement

Metric	Current	After Quick Wins	After Full Optimization
Performance	...	...	...
LCP	...	...	...
CLS	...	...	...

Implementation Snippets

For the top 5 fixes, provide copy-paste-ready code or configuration.