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addyosmani/web-quality-audit

Name: web-quality-audit
Author: addyosmani

skills/web-quality-audit/SKILL.md

npx skillsauth add addyosmani/web-quality-skills web-quality-audit

Clean

TrivyContainer and dependency vulnerability scanner

Clean

SemgrepStatic code analysis for vulnerabilities

Clean

mcp-scan (Snyk)Model Context Protocol security validation

Skipped

Snyk (dep)Open source security scanning

Skipped

Socket.devSupply chain security analysis

Skipped

VirusTotalMulti-engine malware detection

Skipped

CrowdStrikeAdvanced threat intelligence

Skipped

OSV-ScannerOpen Source Vulnerability database check

Skipped

OWASP Dep-Check

Web quality audit

Comprehensive quality review based on Google Lighthouse audits. Covers Performance, Accessibility, SEO, and Best Practices across 150+ checks.

Lighthouse v13 note (Oct 2025+). Lighthouse has migrated the Performance category from per-opportunity audits to Performance Insight Audits (announcement). Several individual audit names this skill historically referenced — First Meaningful Paint, No Document Write, Uses Passive Event Listeners, Uses Rel Preload — have been removed or merged. The underlying advice is unchanged and still applies; only the report format moved. The CLS-related audits ("layout shifts", "non-composited animations", "unsized images") are now consolidated into a single cls-culprits-insight, and image audits are merged into image-delivery-insight. Treat older Lighthouse JSON output as a superset, not a contradiction.

How it works

Analyze the provided code/project for quality issues
Categorize findings by severity (Critical, High, Medium, Low)
Provide specific, actionable recommendations
Include code examples for fixes

Audit categories

Performance (40% of typical issues)

Core Web Vitals — Must pass for good page experience:

LCP (Largest Contentful Paint) < 2.5s. The largest visible element must render quickly. Optimize images, fonts, and server response time.
INP (Interaction to Next Paint) < 200ms. User interactions must feel instant. Reduce JavaScript execution time and break up long tasks.
CLS (Cumulative Layout Shift) < 0.1. Content must not jump around. Set explicit dimensions on images, embeds, and ads.

Resource Optimization:

Compress images. Use WebP/AVIF with fallbacks. Serve correctly sized images via srcset.
Minimize JavaScript. Remove unused code. Use code splitting. Defer non-critical scripts.
Optimize CSS. Extract critical CSS. Remove unused styles. Avoid @import.
Efficient fonts. Use font-display: swap. Preload critical fonts. Subset to needed characters.

Loading Strategy:

Preconnect to origins. Add <link rel="preconnect"> for third-party domains.
Preload critical assets. LCP images, fonts, and above-fold CSS.
Lazy load below-fold content. Images, iframes, and heavy components.
Cache effectively. Long cache TTLs for static assets. Immutable caching for hashed files.

Accessibility (30% of typical issues)

Perceivable:

Text alternatives. Every <img> has meaningful alt text. Decorative images use alt="".
Color contrast. Minimum 4.5:1 for normal text, 3:1 for large text (WCAG AA).
Don't rely on color alone. Use icons, patterns, or text alongside color indicators.
Captions and transcripts. Video has captions. Audio has transcripts.

Operable:

Keyboard accessible. All functionality available via keyboard. No keyboard traps.
Focus visible. Clear focus indicators on all interactive elements.
Skip links. Provide "Skip to main content" for keyboard users.
Sufficient time. Users can extend time limits. No auto-advancing content without controls.

Understandable:

Page language. Set lang attribute on <html>.
Consistent navigation. Same navigation structure across pages.
Error identification. Form errors clearly described and associated with fields.
Labels and instructions. All form inputs have associated labels.

Robust:

Valid HTML. No duplicate IDs. Properly nested elements.
ARIA used correctly. Prefer native elements. ARIA roles match behavior.
Name, role, value. Interactive elements have accessible names and correct roles.

SEO (15% of typical issues)

Crawlability:

Valid robots.txt. Doesn't block important resources.
XML sitemap. Lists all important pages. Submitted to Search Console.
Canonical URLs. Prevent duplicate content issues.
No noindex on important pages. Check meta robots and headers.

On-Page SEO:

Unique title tags. 50-60 characters. Primary keyword included.
Meta descriptions. 150-160 characters. Compelling and unique.
Heading hierarchy. Single <h1>. Logical heading structure.
Descriptive link text. Not "click here" or "read more".

Technical SEO:

Mobile-friendly. Responsive design. Tap targets ≥ 48px.
HTTPS. Secure connection required.
Fast loading. Performance directly impacts ranking.
Structured data. JSON-LD for rich snippets (Article, Product, FAQ, etc.).

Best practices (15% of typical issues)

Security:

HTTPS everywhere. No mixed content. HSTS enabled.
No vulnerable libraries. Keep dependencies updated.
CSP headers. Content Security Policy to prevent XSS.
No exposed source maps. In production builds.

Modern Standards:

No deprecated APIs. Replace document.write, synchronous XHR, etc.
Valid doctype. Use <!DOCTYPE html>.
Charset declared. <meta charset="UTF-8"> as first element in <head>.
No browser errors. Clean console. No CORS issues.

UX Patterns:

No intrusive interstitials. Especially on mobile.
Clear permission requests. Only ask when needed, with context.
No misleading buttons. Buttons do what they say.

Severity levels

| Level | Description | Action | |-------|-------------|--------| | Critical | Security vulnerabilities, complete failures | Fix immediately | | High | Core Web Vitals failures, major a11y barriers | Fix before launch | | Medium | Performance opportunities, SEO improvements | Fix within sprint | | Low | Minor optimizations, code quality | Fix when convenient |

Audit output format

When performing an audit, structure findings as:

## Audit results

### Critical issues (X found)
- **[Category]** Issue description. File: `path/to/file.js:123`
  - **Impact:** Why this matters
  - **Fix:** Specific code change or recommendation

### High priority (X found)
...

### Summary
- Performance: X issues (Y critical)
- Accessibility: X issues (Y critical)
- SEO: X issues
- Best Practices: X issues

### Recommended priority
1. First fix this because...
2. Then address...
3. Finally optimize...

Quick checklist

Before every deploy

[ ] Core Web Vitals passing
[ ] No accessibility errors (axe/Lighthouse)
[ ] No console errors
[ ] HTTPS working
[ ] Meta tags present

Weekly review

[ ] Check Search Console for issues
[ ] Review Core Web Vitals trends
[ ] Update dependencies
[ ] Test with screen reader

Monthly deep dive

[ ] Full Lighthouse audit
[ ] Performance profiling
[ ] Accessibility audit with real users
[ ] SEO keyword review

References

For detailed guidelines on specific areas:

Performance Optimization
Core Web Vitals
Accessibility
SEO
Best Practices

addyosmani/web-quality-audit

skills/web-quality-audit/SKILL.md

Comprehensive web quality audit covering performance, accessibility, SEO, and best practices. Use when asked to "audit my site", "review web quality", "run lighthouse audit", "check page quality", or "optimize my website".

1,875 stars

development

Updated May 8, 2026

$ install --global

skillsauth

npx skillsauth add addyosmani/web-quality-skills web-quality-audit

Install 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.

Scanners Passed

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: May 8, 2026, 3:54 AM167.8s2 files scanned

SKILL.md

name:: web-quality-audit
description:: Comprehensive web quality audit covering performance, accessibility, SEO, and best practices. Use when asked to "audit my site", "review web quality", "run lighthouse audit", "check page quality", or "optimize my website".
license:: MIT
author:: web-quality-skills
version:: 1.0

Web quality audit

Comprehensive quality review based on Google Lighthouse audits. Covers Performance, Accessibility, SEO, and Best Practices across 150+ checks.

Lighthouse v13 note (Oct 2025+). Lighthouse has migrated the Performance category from per-opportunity audits to Performance Insight Audits (announcement). Several individual audit names this skill historically referenced — First Meaningful Paint, No Document Write, Uses Passive Event Listeners, Uses Rel Preload — have been removed or merged. The underlying advice is unchanged and still applies; only the report format moved. The CLS-related audits ("layout shifts", "non-composited animations", "unsized images") are now consolidated into a single cls-culprits-insight, and image audits are merged into image-delivery-insight. Treat older Lighthouse JSON output as a superset, not a contradiction.

How it works

Analyze the provided code/project for quality issues
Categorize findings by severity (Critical, High, Medium, Low)
Provide specific, actionable recommendations
Include code examples for fixes

Audit categories

Performance (40% of typical issues)

Core Web Vitals — Must pass for good page experience:

LCP (Largest Contentful Paint) < 2.5s. The largest visible element must render quickly. Optimize images, fonts, and server response time.
INP (Interaction to Next Paint) < 200ms. User interactions must feel instant. Reduce JavaScript execution time and break up long tasks.
CLS (Cumulative Layout Shift) < 0.1. Content must not jump around. Set explicit dimensions on images, embeds, and ads.

Resource Optimization:

Compress images. Use WebP/AVIF with fallbacks. Serve correctly sized images via srcset.
Minimize JavaScript. Remove unused code. Use code splitting. Defer non-critical scripts.
Optimize CSS. Extract critical CSS. Remove unused styles. Avoid @import.
Efficient fonts. Use font-display: swap. Preload critical fonts. Subset to needed characters.

Loading Strategy:

Preconnect to origins. Add <link rel="preconnect"> for third-party domains.
Preload critical assets. LCP images, fonts, and above-fold CSS.
Lazy load below-fold content. Images, iframes, and heavy components.
Cache effectively. Long cache TTLs for static assets. Immutable caching for hashed files.

Accessibility (30% of typical issues)

Perceivable:

Text alternatives. Every <img> has meaningful alt text. Decorative images use alt="".
Color contrast. Minimum 4.5:1 for normal text, 3:1 for large text (WCAG AA).
Don't rely on color alone. Use icons, patterns, or text alongside color indicators.
Captions and transcripts. Video has captions. Audio has transcripts.

Operable:

Keyboard accessible. All functionality available via keyboard. No keyboard traps.
Focus visible. Clear focus indicators on all interactive elements.
Skip links. Provide "Skip to main content" for keyboard users.
Sufficient time. Users can extend time limits. No auto-advancing content without controls.

Understandable:

Page language. Set lang attribute on <html>.
Consistent navigation. Same navigation structure across pages.
Error identification. Form errors clearly described and associated with fields.
Labels and instructions. All form inputs have associated labels.

Robust:

Valid HTML. No duplicate IDs. Properly nested elements.
ARIA used correctly. Prefer native elements. ARIA roles match behavior.
Name, role, value. Interactive elements have accessible names and correct roles.

SEO (15% of typical issues)

Crawlability:

Valid robots.txt. Doesn't block important resources.
XML sitemap. Lists all important pages. Submitted to Search Console.
Canonical URLs. Prevent duplicate content issues.
No noindex on important pages. Check meta robots and headers.

On-Page SEO:

Unique title tags. 50-60 characters. Primary keyword included.
Meta descriptions. 150-160 characters. Compelling and unique.
Heading hierarchy. Single <h1>. Logical heading structure.
Descriptive link text. Not "click here" or "read more".

Technical SEO:

Mobile-friendly. Responsive design. Tap targets ≥ 48px.
HTTPS. Secure connection required.
Fast loading. Performance directly impacts ranking.
Structured data. JSON-LD for rich snippets (Article, Product, FAQ, etc.).

Best practices (15% of typical issues)

Security:

HTTPS everywhere. No mixed content. HSTS enabled.
No vulnerable libraries. Keep dependencies updated.
CSP headers. Content Security Policy to prevent XSS.
No exposed source maps. In production builds.

Modern Standards:

No deprecated APIs. Replace document.write, synchronous XHR, etc.
Valid doctype. Use <!DOCTYPE html>.
Charset declared. <meta charset="UTF-8"> as first element in <head>.
No browser errors. Clean console. No CORS issues.

UX Patterns:

No intrusive interstitials. Especially on mobile.
Clear permission requests. Only ask when needed, with context.
No misleading buttons. Buttons do what they say.

Severity levels

Audit output format

When performing an audit, structure findings as:

## Audit results

### Critical issues (X found)
- **[Category]** Issue description. File: `path/to/file.js:123`
  - **Impact:** Why this matters
  - **Fix:** Specific code change or recommendation

### High priority (X found)
...

### Summary
- Performance: X issues (Y critical)
- Accessibility: X issues (Y critical)
- SEO: X issues
- Best Practices: X issues

### Recommended priority
1. First fix this because...
2. Then address...
3. Finally optimize...

Quick checklist

Before every deploy

[ ] Core Web Vitals passing
[ ] No accessibility errors (axe/Lighthouse)
[ ] No console errors
[ ] HTTPS working
[ ] Meta tags present

Weekly review

[ ] Check Search Console for issues
[ ] Review Core Web Vitals trends
[ ] Update dependencies
[ ] Test with screen reader

Monthly deep dive

[ ] Full Lighthouse audit
[ ] Performance profiling
[ ] Accessibility audit with real users
[ ] SEO keyword review

References

For detailed guidelines on specific areas:

Performance Optimization
Core Web Vitals
Accessibility
SEO
Best Practices

Related Skills

addyosmani/seo

data-ai

VerifiedTrustedCommunity

Optimize for search engine visibility and ranking. Use when asked to "improve SEO", "optimize for search", "fix meta tags", "add structured data", "sitemap optimization", or "search engine optimization".

1,875SKILL.mdUpdated Mar 27, 2026

addyosmani/performance

development

VerifiedTrustedCommunity

Optimize web performance for faster loading and better user experience. Use when asked to "speed up my site", "optimize performance", "reduce load time", "fix slow loading", "improve page speed", or "performance audit".

1,875SKILL.mdUpdated Mar 27, 2026

addyosmani/performance

addyosmani/core-web-vitals

development

VerifiedTrustedCommunity

Optimize Core Web Vitals (LCP, INP, CLS) for better page experience and search ranking. Use when asked to "improve Core Web Vitals", "fix LCP", "reduce CLS", "optimize INP", "page experience optimization", or "fix layout shifts".

1,875SKILL.mdUpdated Mar 27, 2026

addyosmani/core-web-vitals

addyosmani/best-practices

development

VerifiedTrustedCommunity

Apply modern web development best practices for security, compatibility, and code quality. Use when asked to "apply best practices", "security audit", "modernize code", "code quality review", or "check for vulnerabilities".

1,875SKILL.mdUpdated Mar 27, 2026

addyosmani/best-practices

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Install manually

Choose your platform

# Clone the repo
git clone https://github.com/addyosmani/web-quality-skills.git

# Copy into Claude Code skills folder (global)
cp -r web-quality-skills/skills/web-quality-audit ~/.claude/skills/

Claude Code Skills — official skills path docs.

Repository

addyosmani/web-quality-skills

1,875 stars

Compatible with

Claude Code

OpenAI Codex CLI

ChatGPT