Use the following checklist for pre-launch websites or websites that are already live. This checklist is for the front-end of your website or blog, and are based on Google’s Progressive Web App Checklist.
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Performance

General

  • HTTP/2 is being used
  • CDN is used for assets
  • CDN is used for static resources
  • Cookie-less domain used for static files
  • DNS prefetching is used
    • <link rel="preload" as="script">
    • <link rel="dns-prefetch">

Resources

  • JavaScript files combined into one file
  • JavaScript is minified
  • JavaScript is compressed
  • No inline JavaScript
  • CSS files combined into one file
  • CSS is minified
  • CSS is compressed
  • CSS has no use of @import
  • No inline CSS
  • HTML is minified
  • Static files are compressed with gzip or brotli
  • Static files are server-side pre-compressed
  • HTML is compressed with gzip or brotli
  • Usage of correct image formats
  • Usage of responsive images
  • Images are optimized
  • Image size served is only what is required
  • Image are cached in the browser
  • SVG files are minized
  • SVG files are used where possible
  • Only fonts that are used are loaded
  • Browser cache is used efficiently
  • ETags is not used
  • Expires, cache-control and max-age headers for static resources is set to 1 year
  • Asychronous or deferred loading of non-critical content
  • Tracking scripts loaded asynchronously

Measurements

Usually I measure the main pages of a project here.

  • Count of all files
  • Size of all files combined
  • Download time of the page
  • Google Page Speed analysis (Desktop, Mobile and Mobile UX; x of 100)
  • SpeedIndex

Rendering Performance

  • Intrinsic image sizes are specified in the markup
  • CSS is loaded in the document head
  • Scripts are loaded at the end of the document
  • Scripts are loaded with defer-attribute
  • Scripts are loaded in the document head after styles are loaded
  • Scrolling is possible with 60fps
  • No usage of document.write
  • CSS animation causing layout(reflow) is not heavily used

Device performance

  • CPU usage
  • Memory usage
  • GPU usage

Cross-Browser

  • Website is loading on all current desktop browsers (Safari, Firefox, Chrome, IE11, EDGE)
  • Website is loading on all current mobile browser (Chrome for Android, iOS Safari)
  • For Shops: Checkout is usable on all necessary devices and browsers
  • Viewport Meta Tag is used correctly
  • Usage of correct input types

SEO

  • Pages can be indexed
  • Mobile version of website is available
  • Sitemap is available
  • Structured-Data is used where possible
  • Headlines used
  • Headlines in correct order
  • Meta descriptions used
  • Meta keywords used
  • Meta title is filled correctly
  • Keywords used in headlines
  • Images use the alt-attribute
  • Links use a title-attribute
  • Links in navigation do not use title-attribute
  • No Duplicate Content
  • Usage of absolute URLs
  • Internal links point to HTTPS version of page
  • Redirects are done with 301
  • No 404-errors
  • No 500-errors
  • Canonical Tags are used if applicable
  • Ratio of code and content is around 25% for shop pages and 50% for content pages
  • Affiliate links have rel="nofollow"
  • Website uses HTTPS

Accessibility

  • Color Contrast is good (WCAG 2.0)
  • WAI-ARIA roles are used
  • Usage of accessible elements like nav, footer, aside
  • URLs are accessible
  • Keyboard accessibility is available
  • Correct input types are used

Security

  • HTTPS is used
  • There is no mixed content on the pages
  • External plugins and trackings get loaded via HTTPS
  • Robots.txt is in use
  • Cross-Site-Scripting is not possible
  • HSTS Header is set
  • Content-Security-Policy is set and only allows specific hosts and no inline scripts

More

  • Strict usage of domain with or without www
  • Correct language set in HTML tag
  • Charset is set
  • HTML is valid
  • 404-page is available
  • A special print style sheet is in place

Server

  • Correct language set by the server
  • Correct content types set by the server