Guidelines
What we check, and why it matters
Every finding on a report cites one of the W3C Web Sustainability Guidelines. These pages explain each one and list the measured pages that currently fail it, drawn from the 60 most recently measured pages.
- Optimize media to reduce resource useShip images and video at the size and format the page actually needs.35 failing
- Use optimized web typographyUse as few font files as the design genuinely needs, subset to the glyphs used.23 failing
- Set goals based on performance and energy impactDecide what the page is allowed to weigh, and hold the line in review.26 failing
- Minify and remove unused codeSend only the code the page runs, minified and compressed.42 failing
- Modularize bandwidth-heavy componentsLoad heavy components when they are needed, not on first paint.42 failing
- Treat third parties the same as first partiesHold third-party code to the same weight budget as your own.43 failing
- Ensure code follows good semantic practicesUse HTML elements for what they mean, and keep the DOM small.17 failing
- Use sustainable hostingRun the site on infrastructure powered by renewable energy.—
- Optimize caching and support offline accessLet repeat visits reuse what the browser already has.10 failing
- Setup necessary error pages and redirection linksKeep links working: no broken references, no redirect chains.16 failing
- Reduce data transfer with compressionCompress every text response on the wire.29 failing