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Prompts Website Performance Audit Optimizer

developer analysis template risk: medium

Website Performance Audit Optimizer

Acts as a web performance specialist to analyze a given site URL, assess Core Web Vitals and areas like images, fonts, JavaScript, CSS, and caching, then provide a quick summary, p…

  • External action: medium

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.

INPUTS

url REQUIRED

Site URL to analyze

e.g. https://example.com

current_known_issues

Optional list of current known issues

e.g. slow on mobile, images are huge

target_scores

Optional target performance scores

e.g. LCP under 2.5s, CLS under 0.1

hosting

Hosting platform or setup

e.g. Vercel

REQUIRED CONTEXT

  • Site URL

OPTIONAL CONTEXT

  • Current known issues
  • Target scores
  • Hosting

TOOLS REQUIRED

  • browser

ROLES & RULES

Role assignments

  • You are a web performance specialist.

EXPECTED OUTPUT

Format
markdown
Schema
markdown_sections · Quick Summary (for the client/stakeholder), Optimization Roadmap, Expected Score Improvement, Implementation Snippets
Constraints
  • Quick Summary section with 3-4 sentences
  • Optimization Roadmap as table with columns: Priority, Issue, Impact, Effort, How to Fix
  • Expected Score Improvement as table with columns: Metric, Current, After Quick Wins, After Full Optimization
  • Implementation Snippets for top 5 fixes with copy-paste code
  • Sections for Core Web Vitals, Image Optimization, Font Optimization, JavaScript Analysis, CSS Analysis, Caching & Delivery

SUCCESS CRITERIA

  • Analyze Core Web Vitals for LCP, FID/INP, CLS.
  • List image optimization issues and fixes.
  • Provide font optimization recommendations.
  • Analyze JavaScript bundle size and issues.
  • Analyze CSS unused and blocking issues.
  • Check caching, CDN, and compression.

FAILURE MODES

  • May provide generic advice without site-specific analysis.
  • Might ignore optional inputs like hosting or known issues.
  • Could invent metrics or scores without real data.

CAVEATS

Dependencies
  • Site URL
  • Current known issues
  • Target scores
  • Hosting
Missing context
  • Specific performance analysis tools or APIs (e.g., Lighthouse, PageSpeed Insights, WebPageTest).
  • Access method for site data (e.g., simulate analysis or require real-time fetch).
Ambiguities
  • Method for obtaining current metrics (e.g., Core Web Vitals scores, bundle sizes) not specified (assumes external analysis tool).
  • Integration of optional inputs (Current known issues, Target scores, Hosting) not detailed.

QUALITY

OVERALL
0.92
CLARITY
0.92
SPECIFICITY
0.95
REUSABILITY
0.94
COMPLETENESS
0.88

IMPROVEMENT SUGGESTIONS

  • Add instruction: 'Simulate or use tools like Google PageSpeed Insights and Lighthouse to measure current metrics, bundle sizes, etc.'
  • Clarify optional inputs: 'Incorporate Current known issues into analysis; aim for Target scores; tailor hosting recommendations based on provided Hosting info.'
  • Expand Output Format to include 'Deep Dive Details' section for full analysis areas beyond top 5 fixes.

USAGE

Copy the prompt above and paste it into your AI of choice — Claude, ChatGPT, Gemini, or anywhere else you're working. Replace any placeholder sections with your own context, then ask for the output.

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