web-performance
Diagnose and fix website speed — Core Web Vitals (LCP, INP, CLS), bundle size, images, fonts, caching, and rendering strategy — for Next.js, React/Vite, Vue/Nuxt, Astro, and static sites. Use whenever the user says the site is slow, "website lemot", wants a better Lighthouse/PageSpeed score, mentions Core Web Vitals, large bundles, or is preparing a site for launch.
Target: React / Next.js. Automatically collected · unverified.
Excerpt from the author’s documentation
Extracted from a fixed version of SKILL.md in its original language. This is the author’s documentation; installation, compatibility and runtime results have not been verified by this site.
Read the original English text
Topics in the source
- Web Performance
- 1. Measure
- 2. Fix by metric
- 3. Re-measure and report
Measure → fix the biggest bottleneck → measure again. Never optimize blind. Production build only (npm run build && npm run start / preview). Dev mode numbers are meaningless. Lighthouse (mobile preset): npx lighthouse --preset=perf --form-factor=mobile --output=json --output-path=./lh.json --chrome-flags="--headless" if Chrome is available; otherwise ask the user to run PageSpeed Insights and paste the result. Bundle: npx vite-bundle-visualizer, ANALYZE=true with @next/bundle-analyzer, or npx source-map-explorer 'dist//.js'. Note the baseline: LCP, INP/TBT, CLS, total JS (gzipped), page weight. Targets: LCP . Remove render-blocking CSS/JS in ; inline critical CSS if needed. Server: use SSG/ISR or cache HTML for pages that don't need per-request data; check TTFB. preconnect to required third-party origins (fonts CDN, API). CLS (layout jumps) width/height or aspect-ratio on every image, video, iframe, ad slot. Fonts: font-display: swap + size-adjusted fallback (next/font does this), or optional. Don't insert banners/content above existing content after load; reserve space. INP (slow interactions) Find long tasks (> 50ms). Break up heavy handlers; defer non-urgent work (requestIdleCa
This is an excerpt. Refer to the complete source and its current requirements.
- Source repository
- KILN-skills/kiln
- Source file
- skills/web-performance/SKILL.md
- Fixed revision
- 555d7ea59d05910b4ef6fb39780da5f906be832b
Sources and evidence
This record was collected automatically. Its documentation, suitability and runtime behavior have not been manually verified.
Author: KILN-skills/kiln · original repository metadata. Documentation review: Not reviewed. Last source check: 2026-11-10T04:00:15.500Z.
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License and attribution
MIT. Third-party content and copyright remain with their authors. Refer to the original license and terms.
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