Here's a list of Lighthouse Performance Audits that Google Chrome Lighthouse, PageSpeed Insights, and other Lighthouse powered tools recommend to improve performance.
Opportunities
Eliminate render-blocking resources: This audit suggests removing or deferring resources (such as CSS and JavaScript) that block the rendering of a webpage, allowing the page to load and display faster.
Properly size images: This audit recommends optimizing image sizes to ensure they are not larger than necessary, reducing the amount of data that needs to be downloaded and improving page load times.
Defer offscreen images: This audit advises delaying the loading of images that are not immediately visible on the screen, improving the initial load time of the page.
Minify CSS: This audit suggests removing unnecessary characters and spaces from CSS files, reducing their file size and improving network efficiency.
Minify JavaScript: This audit recommends removing unnecessary characters, spaces, and comments from JavaScript files, reducing their file size and improving network efficiency.
Remove unused CSS: This audit identifies and suggests removing CSS rules that are not being used on the page, reducing file size and improving performance.
Efficiently encode images: This audit recommends using efficient image encoding formats, such as WebP or JPEG XR, to reduce image file sizes without significant loss of quality.
Serve images in modern formats: This audit suggests serving images in modern formats, such as WebP, to take advantage of their superior compression and smaller file sizes.
Enable text compression: This audit advises enabling text compression using techniques like Gzip or Brotli to reduce the size of text-based resources sent over the network.
Preconnect to required origins: This audit recommends establishing early connections to required origins (such as third-party domains) to reduce the latency of subsequent requests.
Reduce server response times (TTFB): This audit suggests optimizing server configurations, caching, and backend processes to minimize the time it takes for the server to respond to a request (Time To First Byte).
Avoid multiple page redirects: This audit advises minimizing or eliminating unnecessary redirects, as each redirect adds additional time for the browser to fetch the requested resource.
Preload key requests: This audit recommends preloading important resources that will be needed by the page, reducing the time required for subsequent requests.
Use video formats for animated content: This audit suggests using video formats (such as WebM) instead of animated GIFs for better performance and smaller file sizes.
Reduce the impact of third-party code: This audit advises minimizing the usage and impact of third-party code (such as analytics or advertising scripts) to prevent it from slowing down the page.
Avoid non-composited animations: This audit suggests using animations that can be offloaded to the GPU for hardware acceleration, ensuring smooth and efficient animation rendering.
Lazy load third-party resources with facade: This audit recommends using lazy loading techniques to defer the loading of third-party resources until they are actually needed, improving the initial page load time.
Diagnostics
Avoid enormous network payloads: This audit warns against large file sizes that can lead to slower downloads and negatively impact the page load performance.
Serve static assets with an efficient cache policy: This audit advises configuring cache policies for static assets (such as images, CSS, and JavaScript) to enable browser caching and reduce the need for repeated downloads.
Avoid an excessive DOM size: This audit identifies a large Document Object Model (DOM) size, which can impact performance, and suggests optimizing the structure and reducing unnecessary elements.
Avoid chaining critical requests: This audit advises reducing the dependency between critical requests, such as scripts or stylesheets, to improve parallelism and avoid delays in rendering.
User Timing marks and measures: This audit recommends using the User Timing API to measure and optimize performance-critical parts of the code.
Reduce JavaScript execution time: This audit suggests optimizing JavaScript code to reduce the time it takes to execute and improve overall performance.
Minimize main thread work: This audit advises minimizing the amount of work performed on the main thread, such as heavy JavaScript calculations or rendering operations, to ensure a smooth user experience.
Ensure text remains visible during webfont load: This audit suggests using techniques like font-display to ensure that text remains visible to users even while web fonts are loading.
Keep request counts low and transfer sizes small: This audit recommends minimizing the number of network requests and reducing the size of transferred data to improve performance.
Ensure the page can be restored from the back/forward cache: This audit advises optimizing the page so that it can be efficiently restored from the back/forward cache, reducing the need for full page reloads and improving navigation speed.