Frontend Development Checklist for Websites

A comprehensive frontend development checklist to optimize website performance, accessibility, SEO, and security. Use this guide to ensure your site meets modern standards, performs well across devices, and provides an excellent user experience while maintaining security and compliance.

Frontend Development Checklist for Websites
Photo by Andrew Neel / Unsplash

Building a fast, secure, and user-friendly website is crucial in today's digital landscape. This comprehensive frontend development checklist is designed to help developers ensure their websites meet modern performance standards, provide optimal user experience, and comply with the latest accessibility, SEO, and security guidelines. By following this checklist, you can systematically improve the quality of your website, ensuring it performs well across devices and browsers while maintaining a high level of security and accessibility for all users.

Use this checklist during the development process or as part of a pre-launch audit to catch potential issues and optimize your website's frontend structure.

Performance

General

  • [ ] HTTP/2 or HTTP/3 is being used
  • [ ] CDN is used for assets and static resources
  • [ ] Cookie-less domain used for static files (where applicable)
  • [ ] DNS prefetching is used for external resources
    • [ ] <link rel="preload" as="script" href="..."> for critical scripts
    • [ ] <link rel="dns-prefetch" href="..."> for external domains
    • [ ] <link rel="preconnect" href="..."> for faster connection setup
  • [ ] Resource hints like preload, prefetch, and preconnect are used correctly

Resources

  • [ ] JavaScript files are combined where appropriate to reduce requests
  • [ ] JavaScript is minified and compressed
  • [ ] No inline JavaScript for better caching
  • [ ] Critical CSS is inlined, rest is loaded asynchronously
  • [ ] CSS is minified and compressed
  • [ ] CSS does not use @import
  • [ ] HTML is minified
  • [ ] Static files (JS, CSS, images) are compressed with gzip or brotli
  • [ ] HTML is compressed with gzip or brotli
  • [ ] Correct image formats are used (e.g., WebP, AVIF)
  • [ ] Responsive images (srcset, sizes) are used
  • [ ] Images are optimized for size and quality (use tools like ImageOptim, Squoosh)
  • [ ] Proper caching headers are used for static resources
  • [ ] Asynchronous or deferred loading of non-critical content
  • [ ] Fonts are loaded efficiently (e.g., font-display: swap)
  • [ ] Lazy loading is used for images and iframes (loading="lazy")
  • [ ] Unused CSS and JS are removed
  • [ ] Only necessary fonts are loaded, avoiding redundant font files
  • [ ] Tracking scripts loaded asynchronously or deferred

Measurements

  • [ ] Count of all files is optimal (no excessive requests)
  • [ ] Size of all files combined is optimized
  • [ ] Page load time is measured and optimized
  • [ ] Lighthouse performance score (Desktop & Mobile)
  • [ ] SpeedIndex and Time to Interactive (TTI)
  • [ ] Largest Contentful Paint (LCP) and Cumulative Layout Shift (CLS) are optimized

Rendering Performance

  • [ ] Intrinsic image sizes are specified (width, height attributes on <img>)
  • [ ] Critical CSS is loaded first
  • [ ] JavaScript is deferred (defer) or loaded asynchronously (async)
  • [ ] No blocking resources are loaded above-the-fold
  • [ ] Scroll performance is optimized (60fps)
  • [ ] Minimal usage of heavy CSS animations (especially those causing reflows)

Device Performance

  • [ ] CPU usage is optimized (no excessive JS execution)
  • [ ] Memory usage is monitored and optimized (avoid memory leaks)
  • [ ] GPU usage is efficient (avoid redundant animations)
  • [ ] Battery usage is minimal for mobile devices (avoid excessive polling)

Cross-Browser

  • [ ] Website is functional on all major desktop browsers (Chrome, Firefox, Safari, Edge)
  • [ ] Website is functional on all major mobile browsers (iOS Safari, Chrome for Android)
  • [ ] Checkout (for e-commerce sites) is usable across devices and browsers
  • [ ] Viewport Meta Tag is set correctly (<meta name="viewport" content="width=device-width, initial-scale=1">)
  • [ ] Correct input types are used for form elements (email, number, tel, etc.)

SEO

  • [ ] Pages are indexable (robots.txt and meta directives)
  • [ ] Mobile-friendly version of the website (Mobile-First design)
  • [ ] XML Sitemap is present and updated
  • [ ] Structured Data (Schema.org) is implemented where applicable
  • [ ] Headers (H1, H2, etc.) are used semantically and in the correct order
  • [ ] Meta descriptions are unique and optimized
  • [ ] Meta keywords are used (though not heavily relied on by search engines)
  • [ ] Title tags are filled correctly and optimized for SEO
  • [ ] Images have alt attributes for accessibility and SEO
  • [ ] No unnecessary title attributes on links (only when adding context)
  • [ ] No duplicate content issues (canonical tags are used properly)
  • [ ] Usage of absolute URLs where necessary
  • [ ] Internal links point to the HTTPS version of pages
  • [ ] 301 redirects are used correctly
  • [ ] No 404 or server errors (500)
  • [ ] HTTPS is enforced, and the website is fully secure
  • [ ] Page content-to-code ratio is optimized for better SEO
  • [ ] Affiliate links use rel="nofollow"
  • [ ] Canonical tags are correctly set

Accessibility

  • [ ] WCAG 2.1 standards are followed
  • [ ] Color contrast meets accessibility standards (use tools to check)
  • [ ] ARIA roles are used where appropriate
  • [ ] Landmarks (e.g., <nav>, <footer>, <main>) are used for navigation
  • [ ] URLs are human-readable and accessible
  • [ ] Keyboard navigation is fully supported (no inaccessible elements)
  • [ ] Forms have appropriate labels and input types (e.g., email, tel, etc.)
  • [ ] Focus states are clearly visible
  • [ ] Skip links are present for improved navigation

Security

  • [ ] HTTPS is used throughout the website
  • [ ] No mixed content issues (all resources loaded via HTTPS)
  • [ ] External plugins and tracking scripts are served over HTTPS
  • [ ] A properly configured robots.txt file is present
  • [ ] Cross-Site Scripting (XSS) vulnerabilities are mitigated
  • [ ] Content Security Policy (CSP) is in place to prevent attacks
  • [ ] HSTS headers are used to enforce HTTPS
  • [ ] CSRF protection is implemented where necessary
  • [ ] Forms and inputs are sanitized to avoid SQL injection

Best Practices

  • [ ] Domain consistency (choose either with or without www and enforce it)
  • [ ] Language attribute (lang) is correctly set on the <html> tag
  • [ ] Character set is set (<meta charset="UTF-8">)
  • [ ] HTML and CSS are valid (use validators like W3C Validator)
  • [ ] Custom 404 page is present and useful
  • [ ] Print stylesheets are included for better print output

Server

  • [ ] Correct language headers are set by the server
  • [ ] Correct content-type headers are set by the server
  • [ ] Server response times are optimized (use caching, CDN, etc.)
  • [ ] HTTP security headers (e.g., X-Frame-Options, X-Content-Type-Options, Referrer-Policy) are in place