Website performance
Web performance essentials — Core Web Vitals, image optimisation, lazy loading, resource hints, Cache-Control, compression, font loading, and script loading attributes. Use when improving load speed, caching, images, fonts, or Core Web Vitals on a website.From its SKILL.md
npx -y skills add paulgrape/skill-auditor --skill website-performanceAssembled from the repository path, not quoted from the project. Check it against their README if it does not work.
2 things to look at
- 29 days oldThe repository was created 29 days ago. New is not bad, but a brand new repository carrying a familiar-sounding name is the shape a typosquat arrives in, and there has been no time for anyone else to find a problem with it.
- 0 stars0 stars. Stars are a popularity signal and not a quality one, but at this level it is likely that nobody has read this closely except its author, and you would be relying on your own review.
SKILL.md
1.8 KB, 393 tokens by cl100k_base, as published. Nobody here has run it
Website performance
Core Web Vitals, caching, images, fonts, network behaviour. Curated from the Website Specification — Performance (CC BY 4.0).
Required
- Hit Core Web Vitals at the 75th percentile: LCP <= 2.5s, INP <= 200ms, CLS <= 0.1.
- Serve images in modern formats (WebP, AVIF), sized for the viewport, with explicit dimensions.
- Set
Cache-Control:immutable, max-age=31536000for fingerprinted assets; short/no-cache for HTML. - Compress text responses (brotli where supported, gzip elsewhere); do not recompress media.
Recommended
- Native lazy loading (
loading="lazy") for off-screen images/iframes — never on the LCP element. - Resource hints: preload the LCP image and critical fonts, preconnect to third-party origins.
- Conditional requests: send
ETag/Last-Modified, honourIf-None-Match/If-Modified-Since. - Self-host subsetted WOFF2 fonts with
font-display: swap. - Inline critical CSS; defer the rest.
- Choose the right
<script>attribute:deferfor app code,asyncfor independent third-party,type="module"for modern code. - Serve over HTTP/2 at minimum, HTTP/3 where possible.
Avoid
- HTTP/1.1 workarounds under HTTP/2+: domain sharding and image sprites.
Example
<link rel="preload" as="image" href="/hero.avif" />
<img src="/below-fold.avif" width="800" height="600" loading="lazy" alt="..." />
Full item list and rationale: https://specification.website/checklist/
What ships with it
Read from the repository
Just SKILL.md. No reference files, no scripts.