general.json

{
  "unused_css_rules": "Remove unused rules from stylesheets to reduce unnecessary bytes consumed by network activity. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/unused-css).",
  "uses_webp_images": "Image formats like JPEG 2000, JPEG XR, and WebP often provide better compression than PNG or JPEG, which means faster downloads and less data consumption. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/webp).",
  "offscreen_images": "Consider lazy-loading offscreen and hidden images after all critical resources have finished loading to lower time to interactive. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/offscreen-images).",
  "total_byte_weight": "Large network payloads cost users real money and are highly correlated with long load times. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/network-payloads).",
  "render_blocking_resources": "Resources are blocking the first paint of your page. Consider delivering critical JS/CSS inline and deferring all non-critical JS/styles. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/blocking-resources).",
  "unminified_css": "Minifying CSS files can reduce network payload sizes. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/minify-css).",
  "unminified_javascript": "Minifying JavaScript files can reduce payload sizes and script parse time. [Learn more](https://developers.google.com/speed/docs/insights/MinifyResources).",
  "efficient_animated_content": "Large GIFs are inefficient for delivering animated content. Consider using MPEG4/WebM videos for animations and PNG/WebP for static images instead of GIF to save network bytes. [Learn more](https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/replace-animated-gifs-with-video/)",
  "unused_javascript": "Remove unused JavaScript to reduce bytes consumed by network activity.",
  "uses_long_cache_ttl": "A long cache lifetime can speed up repeat visits to your page. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/cache-policy).",
  "uses_optimized_images": "Optimized images load faster and consume less cellular data. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/optimize-images).",
  "uses_text_compression": "Text-based resources should be served with compression (gzip, deflate or brotli) to minimize total network bytes. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/text-compression).",
  "uses_responsive_images": "Serve images that are appropriately-sized to save cellular data and improve load time. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/oversized-images).",
  "time_to_first_byte": "Time To First Byte identifies the time at which your server sends a response. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/ttfb).",
  "redirects": "Redirects introduce additional delays before the page can be loaded. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/redirects).",
  "user-timings": "Consider instrumenting your app with the User Timing API to measure your app's real-world performance during key user experiences. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/user-timing).",
  "uses-rel-preconnect": "Consider adding preconnect or dns-prefetch resource hints to establish early connections to important third-party origins. [Learn more](https://developers.google.com/web/fundamentals/performance/resource-prioritization#preconnect).",
  "uses-rel-preload": "Consider using <link rel=preload> to prioritize fetching resources that are currently requested later in page load. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/preload).",
  "critical-request-chains": "The Critical Request Chains below show you what resources are loaded with a high priority. Consider reducing the length of chains, reducing the download size of resources, or deferring the download of unnecessary resources to improve page load. [Learn more](https://developers.google.com/web/tools/lighthouse/audits/critical-request-chains).",
  "dom-size": "Browser engineers recommend pages contain fewer than ~1,500 DOM nodes. The sweet spot is a tree depth < 32 elements and fewer than 60 children/parent element. A large DOM can increase memory usage, cause longer [style calculations](https://developers.google.com/web/fundamentals/performance/rendering/reduce-the-scope-and-complexity-of-style-calculations), and produce costly [layout reflows](https://developers.google.com/speed/docs/insights/browser-reflow). [Learn more](https://developers.google.com/web/tools/lighthouse/audits/dom-size).",
  "font-display": "Leverage the font-display CSS feature to ensure text is user-visible while webfonts are loading. [Learn more](https://developers.google.com/web/updates/2016/02/font-display)."
}