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Lighthouse & Performance Optimization

TEXT
Variables detected: ${url}${specific_steps}— replace before using.
Prompt2458 chars · 385 words
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.

Overview

Lighthouse & Performance Optimization is a free prompt on OpenRuna. A curated prompt on OpenRuna for builders using ChatGPT, Claude, and Cursor.

What this prompt does

"Lighthouse & Performance Optimization" is designed to help you get reliable results from AI assistants for real prompt tasks. A curated prompt on OpenRuna for builders using ChatGPT, Claude, and Cursor. It is catalogued in OpenRuna's resource graph so you can discover related prompts, tools, agents, and datasets in one place. Copy the content directly into ChatGPT, Claude, Gemini, or Cursor — or use it as a system prompt / skill instruction where applicable.

Use cases

  • Use "Lighthouse & Performance Optimization" when you need a repeatable prompt for professional workflows without writing instructions from scratch each time.
  • Adapt this prompt for team onboarding — paste into Claude or ChatGPT and iterate on the output with your project context.
  • Combine with related tools and prompts in the same OpenRuna category to build a full stack for your use case.
  • Reference during code review or planning sessions when you want consistent AI-assisted quality bars.

Example output

When you run this prompt, expect structured output similar to:

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 ca…

Outputs vary by model and temperature; treat the first response as a draft and refine with follow-up prompts.

Tips by platform

Claude

In Claude, paste the full prompt as the first user message or add it to Project instructions. Ask Claude to confirm assumptions before executing. For long prompts, use Claude's artifact panel to iterate on structured output.

ChatGPT

In ChatGPT, start a new chat and paste this prompt verbatim. Enable GPT-4o or your preferred model for coding tasks. Use follow-ups like "apply this to [your context]" for best results.

Cursor

In Cursor, add key instructions from this prompt to .cursorrules or a SKILL.md file. Reference it in Agent mode with @ mentions. Keep the original title in comments so teammates can find it on OpenRuna.

Frequently asked questions

What is "Lighthouse & Performance Optimization"?
It is a prompt listed on OpenRuna — A curated prompt on OpenRuna for builders using ChatGPT, Claude, and Cursor. You can copy and adapt it for ChatGPT, Claude, Cursor, or other AI tools.
Is this prompt free to use?
Most OpenRuna resources are open or CC0-licensed. Check the license on this page before commercial use. Premium collections are clearly marked.
How do I get the best results?
Replace any template variables, add your project context, and ask the model to confirm assumptions. Iterate in 2–3 follow-up turns rather than expecting a perfect first response.
Can I use this with Claude and ChatGPT?
Yes. The prompt is model-agnostic text. Tips on this page cover Claude, ChatGPT, and Cursor specifically.
Where can I find related resources?
Scroll to Related resources on this page or browse the category hub on OpenRuna to find connected prompts, tools, and agents in the same topic area.

Related resources