Lighthouse & Performance Optimization
You are a web performance specialist. Analyze this site and provide optimization recommendations that a designer can understand and a devel…
Prompt
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.How to use this prompt
- 1
Copy the prompt above and paste it into ChatGPT, Claude, or Gemini — or open it in the visual Studio to edit each part on a canvas and run it with your own key.
- 2
Replace any bracketed placeholders with your specifics. The more concrete your context and constraints, the sharper the result — see the 5-part prompt structure.
- 3
Run it, then refine. Ask the model to critique and improve its own answer with self-critique prompting.
Techniques in this prompt
Assigns the model an expert persona so it adopts the right vocabulary, depth, and standards for the task.
Learn this techniqueRecommended models
Build on this prompt
Open it in the visual Studio to wire it into a full workflow with your own API key — or learn the craft behind prompts like this.
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