best-practices▌
tech-leads-club/agent-skills · updated May 23, 2026
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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". Do NOT use for accessibility (use web-accessibility), SEO (use seo), performance (use core-web-vitals), or comprehensive multi-area audits (use web-quality-audit).
| name | best-practices |
| description | 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". Do NOT use for accessibility (use web-accessibility), SEO (use seo), performance (use core-web-vitals), or comprehensive multi-area audits (use web-quality-audit). |
| license | MIT |
| metadata | author: web-quality-skills version: '1.0' |
Best practices
Modern web development standards based on Lighthouse best practices audits. Covers security, browser compatibility, and code quality patterns.
Security
HTTPS everywhere
Enforce HTTPS:
<!-- ❌ Mixed content -->
<img src="http://example.com/image.jpg" />
<script src="http://cdn.example.com/script.js"></script>
<!-- ✅ HTTPS only -->
<img src="https://example.com/image.jpg" />
<script src="https://cdn.example.com/script.js"></script>
<!-- ✅ Protocol-relative (will use page's protocol) -->
<img src="//example.com/image.jpg" />
HSTS Header:
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
Content Security Policy (CSP)
<!-- Basic CSP via meta tag -->
<meta
http-equiv="Content-Security-Policy"
content="default-src 'self';
script-src 'self' https://trusted-cdn.com;
style-src 'self' 'unsafe-inline';
img-src 'self' data: https:;
connect-src 'self' https://api.example.com;"
/>
<!-- Better: HTTP header -->
CSP Header (recommended):
Content-Security-Policy:
default-src 'self';
script-src 'self' 'nonce-abc123' https://trusted.com;
style-src 'self' 'nonce-abc123';
img-src 'self' data: https:;
connect-src 'self' https://api.example.com;
frame-ancestors 'self';
base-uri 'self';
form-action 'self';
Using nonces for inline scripts:
<script nonce="abc123">
// This inline script is allowed
</script>
Security headers
# Prevent clickjacking
X-Frame-Options: DENY
# Prevent MIME type sniffing
X-Content-Type-Options: nosniff
# Enable XSS filter (legacy browsers)
X-XSS-Protection: 1; mode=block
# Control referrer information
Referrer-Policy: strict-origin-when-cross-origin
# Permissions policy (formerly Feature-Policy)
Permissions-Policy: geolocation=(), microphone=(), camera=()
No vulnerable libraries
# Check for vulnerabilities
npm audit
yarn audit
# Auto-fix when possible
npm audit fix
# Check specific package
npm ls lodash
Keep dependencies updated:
// package.json
{
"scripts": {
"audit": "npm audit --audit-level=moderate",
"update": "npm update && npm audit fix"
}
}
Known vulnerable patterns to avoid:
// ❌ Prototype pollution vulnerable patterns
Object.assign(target, userInput)
_.merge(target, userInput)
// ✅ Safer alternatives
const safeData = JSON.parse(JSON.stringify(userInput))
Input sanitization
// ❌ XSS vulnerable
element.innerHTML = userInput
document.write(userInput)
// ✅ Safe text content
element.textContent = userInput
// ✅ If HTML needed, sanitize
import DOMPurify from 'dompurify'
element.innerHTML = DOMPurify.sanitize(userInput)
Secure cookies
// ❌ Insecure cookie
document.cookie = "session=abc123";
// ✅ Secure cookie (server-side)
Set-Cookie: session=abc123; Secure; HttpOnly; SameSite=Strict; Path=/
Browser compatibility
Doctype declaration
<!-- ❌ Missing or invalid doctype -->
<html>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<!-- ✅ HTML5 doctype -->
<!DOCTYPE html>
<html lang="en"></html>
</html>
Character encoding
<!-- ❌ Missing or late charset -->
<html>
<head>
<title>Page</title>
<meta charset="UTF-8" />
</head>
<!-- ✅ Charset as first element in head -->
<html>
<head>
<meta charset="UTF-8" />
<title>Page</title>
</head>
</html>
</html>
Viewport meta tag
<!-- ❌ Missing viewport -->
<head>
<title>Page</title>
</head>
<!-- ✅ Responsive viewport -->
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>Page</title>
</head>
Feature detection
// ❌ Browser detection (brittle)
if (navigator.userAgent.includes('Chrome')) {
// Chrome-specific code
}
// ✅ Feature detection
if ('IntersectionObserver' in window) {
// Use IntersectionObserver
} else {
// Fallback
}
// ✅ Using @supports in CSS
@supports (display: grid) {
.container {
display: grid;
}
}
@supports not (display: grid) {
.container {
display: flex;
}
}
Polyfills (when needed)
<!-- Load polyfills conditionally -->
<script>
if (!('fetch' in window)) {
document.write('<script src="/polyfills/fetch.js"><\/script>')
}
</script>
<!-- Or use polyfill.io -->
<script src="https://polyfill.io/v3/polyfill.min.js?features=fetch,IntersectionObserver"></script>
Deprecated APIs
Avoid these
// ❌ document.write (blocks parsing)
document.write('<script src="..."></script>');
// ✅ Dynamic script loading
const script = document.createElement('script');
script.src = '...';
document.head.appendChild(script);
// ❌ Synchronous XHR (blocks main thread)
const xhr = new XMLHttpRequest();
xhr.open('GET', url, false); // false = synchronous
// ✅ Async fetch
const response = await fetch(url);
// ❌ Application Cache (deprecated)
<html manifest="cache.manifest">
// ✅ Service Workers
if ('serviceWorker' in navigator) {
navigator.serviceWorker.register('/sw.js');
}
Event listener passive
// ❌ Non-passive touch/wheel (may block scrolling)
element.addEventListener('touchstart', handler)
element.addEventListener('wheel', handler)
// ✅ Passive listeners (allows smooth scrolling)
element.addEventListener('touchstart', handler, { passive: true })
element.addEventListener('wheel', handler, { passive: true })
// ✅ If you need preventDefault, be explicit
element.addEventListener('touchstart', handler, { passive: false })
Console & errors
No console errors
// ❌ Errors in production
console.log('Debug info') // Remove in production
throw new Error('Unhandled') // Catch all errors
// ✅ Proper error handling
try {
riskyOperation()
} catch (error) {
// Log to error tracking service
errorTracker.captureException(error)
// Show user-friendly message
showErrorMessage('Something went wrong. Please try again.')
}
Error boundaries (React)
class ErrorBoundary extends React.Component {
state = { hasError: false }
static getDerivedStateFromError(error) {
return { hasError: true }
}
componentDidCatch(error, info) {
errorTracker.captureException(error, { extra: info })
}
render() {
if (this.state.hasError) {
return <FallbackUI />
}
return this.props.children
}
}
// Usage
;<ErrorBoundary>
<App />
</ErrorBoundary>
Global error handler
// Catch unhandled errors
window.addEventListener('error', (event) => {
errorTracker.captureException(event.error)
})
// Catch unhandled promise rejections
window.addEventListener('unhandledrejection', (event) => {
errorTracker.captureException(event.reason)
})
Source maps
Production configuration
// ❌ Source maps exposed in production
// webpack.config.js
module.exports = {
devtool: 'source-map', // Exposes source code
}
// ✅ Hidden source maps (uploaded to error tracker)
module.exports = {
devtool: 'hidden-source-map',
}
// ✅ Or no source maps in production
module.exports = {
devtool: process.env.NODE_ENV === 'production' ? false : 'source-map',
}
Performance best practices
Avoid blocking patterns
// ❌ Blocking script
<script src="heavy-library.js"></script>
// ✅ Deferred script
<script defer src="heavy-library.js"></script>
// ❌ Blocking CSS import
@import url('other-styles.css');
// ✅ Link tags (parallel loading)
<link rel="stylesheet" href="styles.css">
<link rel="stylesheet" href="other-styles.css">
Efficient event handlers
// ❌ Handler on every element
items.forEach((item) => {
item.addEventListener('click', handleClick)
})
// ✅ Event delegation
container.addEventListener('click', (e) => {
if (e.target.matches('.item')) {
handleClick(e)
}
})
Memory management
// ❌ Memory leak (never removed)
const handler = () => {
/* ... */
}
window.addEventListener('resize', handler)
// ✅ Cleanup when done
const handler = () => {
/* ... */
}
window.addEventListener('resize', handler)
// Later, when component unmounts:
window.removeEventListener('resize', handler)
// ✅ Using AbortController
const controller = new AbortController()
window.addEventListener('resize', handler, { signal: controller.signal })
// Cleanup:
controller.abort()
Code quality
Valid HTML
<!-- ❌ Invalid HTML -->
<div id="header">
<div id="header">
<!-- Duplicate ID -->
<ul>
<div>Item</div>
<!-- Invalid child -->
</ul>
<a href="/"><button>Click</button></a>
<!-- Invalid nesting -->
<!-- ✅ Valid HTML -->
<header id="site-header"></header>
<ul>
<li>Item</li>
</ul>
<a href="/" class="button">Click</a>
</div>
</div>
Semantic HTML
<!-- ❌ Non-semantic -->
<div class="header">
<div class="nav">
<div class="nav-item">Home</div>
</div>
</div>
<div class="main">
<div class="article">
<div class="title">Headline</div>
</div>
</div>
<!-- ✅ Semantic HTML5 -->
<header>
<nav>
<a href="/">Home</a>
</nav>
</header>
<main>
<article>
<h1>Headline</h1>
</article>
</main>
Image aspect ratios
<!-- ❌ Distorted images -->
<img src="photo.jpg" width="300" height="100" />
<!-- If actual ratio is 4:3, this squishes the image -->
<!-- ✅ Preserve aspect ratio -->
<img src="photo.jpg" width="300" height="225" />
<!-- Actual 4:3 dimensions -->
<!-- ✅ CSS object-fit for flexibility -->
<img src="photo.jpg" style="width: 300px; height: 200px; object-fit: cover;" />
Permissions & privacy
Request permissions properly
// ❌ Request on page load (bad UX, often denied)
navigator.geolocation.getCurrentPosition(success, error)
// ✅ Request in context, after user action
findNearbyButton.addEventListener('click', async () => {
// Explain why you need it
if (await showPermissionExplanation()) {
navigator.geolocation.getCurrentPosition(success, error)
}
})
Permissions policy
<!-- Restrict powerful features -->
<meta http-equiv="Permissions-Policy" content="geolocation=(), camera=(), microphone=()" />
<!-- Or allow for specific origins -->
<meta http-equiv="Permissions-Policy" content="geolocation=(self 'https://maps.example.com')" />
Audit checklist
Security (critical)
- HTTPS enabled, no mixed content
- No vulnerable dependencies (
npm audit) - CSP headers configured
- Security headers present
- No exposed source maps
Compatibility
- Valid HTML5 doctype
- Charset declared first in head
- Viewport meta tag present
- No deprecated APIs used
- Passive event listeners for scroll/touch
Code quality
- No console errors
- Valid HTML (no duplicate IDs)
- Semantic HTML elements used
- Proper error handling
- Memory cleanup in components
UX
- No intrusive interstitials
- Permission requests in context
- Clear error messages
- Appropriate image aspect ratios
Tools
| Tool | Purpose |
|---|---|
npm audit | Dependency vulnerabilities |
| SecurityHeaders.com | Header analysis |
| W3C Validator | HTML validation |
| Lighthouse | Best practices audit |
| Observatory | Security scan |
References
How to use best-practices on Cursor
AI-first code editor with Composer
Prerequisites
Before installing skills in Cursor, ensure your development environment meets these requirements:
- ›Cursor installed and configured on your development machine
- ›Node.js version 16.0+ with npm package manager (verify with
node --version) - ›Active project directory or workspace where you want to add best-practices
Execute installation command
Execute the skills CLI command in your project's root directory to begin installation:
The skills CLI fetches best-practices from GitHub repository tech-leads-club/agent-skills and configures it for Cursor.
Select Cursor when prompted
The CLI will show a list of available agents. Use arrow keys to navigate and space to select Cursor:
Verify installation
Confirm successful installation by checking the skill directory location:
Reload or restart Cursor to activate best-practices. Access the skill through slash commands (e.g., /best-practices) or your agent's skill management interface.
Security & Verification Notice
We perform automated surface-level scans (Gen AI Scanner, Socket, Snyk) during installation. These checks detect common vulnerabilities but do not guarantee complete security. Always review skill source code and verify the publisher's reputation before production use.
Skills execute code in your development environment. Always verify the publisher's identity, review recent commits, and test in isolated environments before production deployment.
List & Monetize Your Skill
Submit your Claude Code skill and start earning
Use Cases▌
Task Automation & Efficiency
Automate repetitive workflows and reduce manual effort
Example
Generate reports, summarize documents, draft communications
Save 3-5 hours per week on routine tasks
Knowledge Enhancement
Learn new skills, understand complex topics, get expert guidance
Example
Explain concepts, provide examples, suggest learning resources
Accelerate learning and skill development by 2x
Quality Improvement
Enhance output quality through reviews, suggestions, and refinements
Example
Review drafts, suggest improvements, catch errors
Improve work quality by 30-40% with less effort
Implementation Guide▌
Prerequisites
- ›Claude Desktop or compatible AI client with skill support
- ›Clear understanding of task or problem to solve
- ›Willingness to iterate and refine outputs
Time Estimate
15-45 minutes depending on use case complexity
Installation Steps
- 1.Install skill using provided installation command
- 2.Test with simple use case relevant to your work
- 3.Evaluate output quality and relevance
- 4.Iterate on prompts to improve results
- 5.Integrate into regular workflow if valuable
Common Pitfalls
- ⚠Expecting perfect results without iteration
- ⚠Not providing enough context in prompts
- ⚠Using skill for tasks outside its intended scope
- ⚠Accepting outputs without review and validation
Best Practices▌
✓ Do
- +Start with clear, specific prompts
- +Provide relevant context and constraints
- +Review and refine all outputs before using
- +Iterate to improve output quality
- +Document successful prompt patterns
✗ Don't
- −Don't use without understanding skill limitations
- −Don't skip validation of outputs
- −Don't share sensitive information in prompts
- −Don't expect skill to replace human judgment
💡 Pro Tips
- ★Be specific about desired format and style
- ★Ask for multiple options to choose from
- ★Request explanations to understand reasoning
- ★Combine AI efficiency with human expertise
When to Use This▌
✓ Use When
Use when skill capabilities match your task, clear ROI on time saved, and you can validate outputs. Best for repetitive tasks, learning, and quality improvement.
✗ Avoid When
Avoid when task requires deep expertise you can't validate, involves sensitive decisions, or when learning process is more valuable than speed of completion.
Learning Path▌
- 1Familiarize yourself with skill capabilities and limitations
- 2Start with low-risk, non-critical tasks
- 3Progress to more complex and valuable use cases
- 4Build expertise through regular use and experimentation
Discussion
Product Hunt–style comments (not star reviews)- No comments yet — start the thread.
Ratings
4.6★★★★★71 reviews- ★★★★★Advait Sanchez· Dec 28, 2024
best-practices reduced setup friction for our internal harness; good balance of opinion and flexibility.
- ★★★★★Noor Shah· Dec 16, 2024
best-practices fits our agent workflows well — practical, well scoped, and easy to wire into existing repos.
- ★★★★★Dhruvi Jain· Dec 12, 2024
best-practices has been reliable in day-to-day use. Documentation quality is above average for community skills.
- ★★★★★Noor Sharma· Dec 12, 2024
I recommend best-practices for anyone iterating fast on agent tooling; clear intent and a small, reviewable surface area.
- ★★★★★Kwame Harris· Dec 12, 2024
best-practices has been reliable in day-to-day use. Documentation quality is above average for community skills.
- ★★★★★Ren Agarwal· Dec 12, 2024
Solid pick for teams standardizing on skills: best-practices is focused, and the summary matches what you get after install.
- ★★★★★Kwame Wang· Nov 19, 2024
best-practices has been reliable in day-to-day use. Documentation quality is above average for community skills.
- ★★★★★Mia Jackson· Nov 7, 2024
We added best-practices from the explainx registry; install was straightforward and the SKILL.md answered most questions upfront.
- ★★★★★Oshnikdeep· Nov 3, 2024
best-practices reduced setup friction for our internal harness; good balance of opinion and flexibility.
- ★★★★★Advait Rao· Nov 3, 2024
Useful defaults in best-practices — fewer surprises than typical one-off scripts, and it plays nicely with `npx skills` flows.
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