tech-leads-club/perf-web-optimization
packages/skills-catalog/skills/(performance)/perf-web-optimization/SKILL.md
Optimize web performance: bundle size, images, caching, lazy loading, and overall page speed. Use when site is slow, reducing bundle size, fixing layout shifts, improving Time to Interactive, or optimizing for Lighthouse scores. Triggers on: web performance, bundle size, page speed, slow site, lazy loading. Do NOT use for Core Web Vitals-specific fixes (use core-web-vitals), running Lighthouse audits (use perf-lighthouse), or Astro-specific optimization (use perf-astro).
$ install --global
skillsauthnpx skillsauth add tech-leads-club/agent-skills perf-web-optimizationInstall this skill globally with one command. Works with Claude Code, Cursor, and Windsurf.
Security Scan Results
3 of 9 scanners reported clean
Some scanners were skipped, did not run, or reported a non-clean status. Review each row below.
3
Scanners Passed
9
Scanners in report
Clean
TrivyContainer and dependency vulnerability scanner
95%
Clean
SemgrepStatic code analysis for vulnerabilities
95%
Clean
mcp-scan (Snyk)Model Context Protocol security validation
95%
Skipped
Snyk (dep)Open source security scanning
50%
Skipped
Socket.devSupply chain security analysis
50%
Skipped
VirusTotalMulti-engine malware detection
50%
Skipped
CrowdStrikeAdvanced threat intelligence
50%
Skipped
OSV-ScannerOpen Source Vulnerability database check
50%
Skipped
OWASP Dep-Check
50%
Last scanned: Apr 27, 2026, 6:45 AM65.7s4 files scanned
SKILL.md
- name:
- perf-web-optimization
- description:
- Optimize web performance: bundle size, images, caching, lazy loading, and overall page speed. Use when site is slow, reducing bundle size, fixing layout shifts, improving Time to Interactive, or optimizing for Lighthouse scores. Triggers on: web performance, bundle size, page speed, slow site, lazy loading. Do NOT use for Core Web Vitals-specific fixes (use core-web-vitals), running Lighthouse audits (use perf-lighthouse), or Astro-specific optimization (use perf-astro).
Web Performance Optimization
Systematic approach: Measure → Identify → Prioritize → Implement → Verify.
Target Metrics
| Metric | Good | Needs Work | Poor | | ------ | ------- | ---------- | ------- | | LCP | < 2.5s | 2.5-4s | > 4s | | INP | < 200ms | 200-500ms | > 500ms | | CLS | < 0.1 | 0.1-0.25 | > 0.25 | | TTFB | < 800ms | 800ms-1.8s | > 1.8s |
Quick Wins
1. Images (usually biggest impact on LCP)
<!-- Hero/LCP image: eager + high priority -->
<img src="/hero.webp" alt="Hero" width="1200" height="600" loading="eager" fetchpriority="high" decoding="async" />
<!-- Below fold: lazy load -->
<img src="/product.webp" alt="Product" width="400" height="300" loading="lazy" decoding="async" />
Always set width and height to prevent CLS.
2. Fonts (common LCP/CLS culprit)
<!-- Preconnect to font origin -->
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
<!-- Non-blocking font load -->
<link
rel="stylesheet"
href="https://fonts.googleapis.com/css2?family=Inter&display=swap"
media="print"
onload="this.media='all'"
/>
3. Third-party Scripts (common INP killer)
<!-- Defer to user interaction -->
<script>
function loadThirdParty() {
// Load analytics, chat widgets, etc.
}
;['scroll', 'click', 'touchstart'].forEach((e) => addEventListener(e, loadThirdParty, { once: true, passive: true }))
setTimeout(loadThirdParty, 5000)
</script>
4. Critical CSS
Inline critical CSS in <head>, defer the rest:
<style>
/* critical styles */
</style>
<link rel="preload" href="/styles.css" as="style" onload="this.rel='stylesheet'" />
Bundle Analysis
# Webpack
npx webpack-bundle-analyzer dist/stats.json
# Vite
npx vite-bundle-visualizer
# Check package size before installing
npx bundlephobia <package-name>
Common heavy packages to replace:
moment(67KB) →date-fns(12KB) ordayjs(2KB)lodash(72KB) → cherry-pick imports or native methods
Code Splitting Patterns
// React lazy
const Chart = lazy(() => import('./Chart'))
// Next.js dynamic
const Admin = dynamic(() => import('./Admin'), { ssr: false })
// Vite/Rollup manual chunks
build: {
rollupOptions: {
output: {
manualChunks: {
vendor: ['react', 'react-dom']
}
}
}
}
Caching Headers
# Static assets (immutable hash in filename)
Cache-Control: public, max-age=31536000, immutable
# HTML (revalidate)
Cache-Control: no-cache
# API responses
Cache-Control: private, max-age=0, must-revalidate
Measurement
For running audits, reading reports, and setting budgets, use the perf-lighthouse skill.
Checklist
Images
- [ ] Modern formats (WebP/AVIF)
- [ ] Responsive
srcset - [ ]
width/heightattributes - [ ]
loading="lazy"below fold - [ ]
fetchpriority="high"on LCP image
JavaScript
- [ ] Bundle < 200KB gzipped
- [ ] Code splitting by route
- [ ] Third-party scripts deferred
- [ ] No unused dependencies
CSS
- [ ] Critical CSS inlined
- [ ] Non-critical CSS deferred
- [ ] No unused CSS
Fonts
- [ ]
font-display: swap - [ ] Preconnect to font origin
- [ ] Subset if possible
Detailed Examples
For in-depth optimization patterns, see:
- references/core-web-vitals.md - Fixing LCP, CLS, INP issues
- references/bundle-optimization.md - Reducing JS bundle size
- references/image-optimization.md - Image formats, responsive images, sharp scripts
Related Skills
tech-leads-club/pr-review
tools
VerifiedTrustedCommunity
Reviews a GitHub pull request and posts inline comments plus one consolidated summary, adapting to any codebase by discovering the project's own test runner, requirement specs, and architecture conventions before running six specialized review agents in parallel. Stack-agnostic across language and framework; targets GitHub PRs via the gh CLI. Use when the user says "review PR 128", "review this PR", "code review this PR", or "check this pull request". Do NOT use for creating PRs or responding to review comments (use gh-address-comments), or debugging failing CI checks (use gh-fix-ci).
4,903SKILL.mdUpdated Jul 19, 2026
tech-leads-club/rails-dev
development
VerifiedTrustedCommunity
Opinionated Rails conventions: rich models, concerns, CRUD-everything, state-as-records, minimal dependencies, Minitest with fixtures. Load this skill BEFORE any code-level thinking, not only before editing a file. It is required the moment a task touches Rails code in ANY way: designing or even just discussing a data model, schema, migration, entity, association, field, validation, class, or method name; writing, planning, reviewing, analyzing, testing, debugging, or refactoring; or proposing any model, table, column, route, or code snippet inline in chat. If you are about to name a model or sketch a column you are already in scope, even in an exploratory back-and-forth where no file is written yet. Do not let a "we're just discussing" framing defer it. Do NOT use for non-Rails backends, NestJS, or general architecture (use nestjs-modular-monolith or coding-guidelines).
4,897SKILL.mdUpdated Jul 18, 2026
tech-leads-club/tlc-spec-driven
testing
VerifiedTrustedCommunity
Feature planning and implementation with 4 adaptive phases — Specify, Design, Tasks, Execute. Auto-sizes depth by complexity. Creates atomic tasks with verification criteria, atomic git commits, and requirement traceability. Features an independent Verifier (author != verifier, evidence-or-zero), persistent decision log (STATE.md), and test-coverage-matrix-driven tests, plus a self-improving lessons layer that turns verification failures into reusable project-local guidance. Stack-agnostic. Use when (1) Planning features (requirements, design, task breakdown), (2) Implementing with verification and atomic commits, (3) Validating or verifying an implementation against a spec. Triggers on "specify feature", "discuss feature", "design", "tasks", "implement", "validate", "verify work", "UAT", "record decision", "pause work", "resume work". Do NOT use for architecture decomposition analysis (use architecture skills) or technical design docs (use create-technical-design-doc).
4,840SKILL.mdUpdated Apr 27, 2026
tech-leads-club/tlc-generative-engine-optimization
development
VerifiedTrustedCommunity
Generative Engine Optimization (GEO) specialist — the technical, on-page publishing work that makes a given page or site discoverable, understandable, trustworthy, quotable, and fresh for AI answer engines (Google AI Overviews, ChatGPT Search, Bing Copilot, Perplexity). Use when asked to 'optimize this page/site for GEO', 'optimize for AI search / answer engines', 'get my page cited by ChatGPT/Perplexity', 'improve AI visibility/citability', 'write an llms.txt', 'add citation-ready structure or schema for AI answers', 'otimizar para busca com IA', or to audit/create/improve a codebase for generative search. Do NOT use for AI-driven SEO content strategy or programmatic pages at scale (use ai-seo), classic keyword/SERP ranking (use seo), accessibility (use web-accessibility), or multi-area site audits (use web-quality-audit).
4,816SKILL.mdUpdated Jul 5, 2026