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Minifying CSS files can reduce network payload sizes. Learn more.

Text-based resources should be served with compression (gzip, deflate or brotli) to minimize total network bytes. Learn more.

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.

Consider using `<link rel=preload>` to prioritize fetching resources that are currently requested later in page load. Learn more.

Consider lazy-loading offscreen and hidden images after all critical resources have finished loading to lower time to interactive. Learn more.

Remove unused JavaScript to reduce bytes consumed by network activity. Learn more.

Resources are blocking the first paint of your page. Consider delivering critical JS/CSS inline and deferring all non-critical JS/styles. Learn more.

Serve images that are appropriately-sized to save cellular data and improve load time. Learn more.

Minifying JavaScript files can reduce payload sizes and script parse time. Learn more.

Remove dead rules from stylesheets and defer the loading of CSS not used for above-the-fold content to reduce unnecessary bytes consumed by network activity. Learn more.

Redirects introduce additional delays before the page can be loaded. Learn more.

Optimized images load faster and consume less cellular data. Learn more.

Remove large, duplicate JavaScript modules from bundles to reduce unnecessary bytes consumed by network activity.

Polyfills and transforms enable legacy browsers to use new JavaScript features. However, many aren't necessary for modern browsers. For your bundled JavaScript, adopt a modern script deployment strategy using module/nomodule feature detection to reduce the amount of code shipped to modern browsers, while retaining support for legacy browsers. Learn More

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

Consider reducing the time spent parsing, compiling, and executing JS. You may find delivering smaller JS payloads helps with this. Learn more.

Lists the longest tasks on the main thread, useful for identifying worst contributors to input delay. Learn more

Third-party code can significantly impact load performance. Limit the number of redundant third-party providers and try to load third-party code after your page has primarily finished loading. Learn more.

These DOM elements contribute most to the CLS of the page.

To set budgets for the quantity and size of page resources, add a budget.json file. Learn more.

Consider instrumenting your app with the User Timing API to measure your app's real-world performance during key user experiences. Learn more.

Consider reducing the time spent parsing, compiling and executing JS. You may find delivering smaller JS payloads helps with this. Learn more

Set a timing budget to help you keep an eye on the performance of your site. Performant sites load fast and respond to user input events quickly. Learn more.

If your robots.txt file is malformed, crawlers may not be able to understand how you want your website to be crawled or indexed. Learn more.

Interactive elements like buttons and links should be large enough (48x48px), and have enough space around them, to be easy enough to tap without overlapping onto other elements. Learn more. Tap targets are too small because there's no viewport meta tag optimized for mobile screens

Font sizes less than 12px are too small to be legible and require mobile visitors to “pinch to zoom” in order to read. Strive to have >60% of page text ≥12px. Learn more. Text is illegible because there's no viewport meta tag optimized for mobile screens.

Add a `<meta name="viewport">` tag to optimize your app for mobile screens. Learn more. No `<meta name="viewport">` tag found

All sites should be protected with HTTPS, even ones that don't handle sensitive data. This includes avoiding mixed content, where some resources are loaded over HTTP despite the initial request being servedover HTTPS. HTTPS prevents intruders from tampering with or passively listening in on the communications between your app and your users, and is a prerequisite for HTTP/2 and many new web platform APIs. Learn more.

Specifying a doctype prevents the browser from switching to quirks-mode. Learn more. Expected publicId to be an empty string

Your app should display some content when JavaScript is disabled, even if it's just a warning to the user that JavaScript is required to use the app. Learn more. The page body should render some content if its scripts are not available.

A themed splash screen ensures a high-quality experience when users launch your app from their homescreens. Learn more. Failures: No manifest was fetched.

If the width of your app's content doesn't match the width of the viewport, your app might not be optimized for mobile screens. Learn more. The viewport size of 980px does not match the window size of 360px.

For ideal appearance on iOS when users add a progressive web app to the home screen, define an `apple-touch-icon`. It must point to a non-transparent 192px (or 180px) square PNG. Learn More.

The browser address bar can be themed to match your site. Learn more. Failures: No manifest was fetched, No `<meta name="theme-color">` tag found.

A maskable icon ensures that the image fills the entire shape without being letterboxed when installing the app on a device. Learn more. No manifest was fetched

Add a `<meta name="viewport">` tag to optimize your app for mobile screens. Learn more. No `<meta name="viewport">` tag found

If you've already set up HTTPS, make sure that you redirect all HTTP traffic to HTTPS in order to enable secure web features for all your users. Learn more.

A service worker enables your web app to be reliable in unpredictable network conditions. Learn more. No usable web app manifest found on page.

If you're building a Progressive Web App, consider using a service worker so that your app can work offline. Learn more.

A fast page load over a cellular network ensures a good mobile user experience. Learn more.

The service worker is the technology that enables your app to use many Progressive Web App features, such as offline, add to homescreen, and push notifications. Learn more.

All sites should be protected with HTTPS, even ones that don't handle sensitive data. This includes avoiding mixed content, where some resources are loaded over HTTP despite the initial request being servedover HTTPS. HTTPS prevents intruders from tampering with or passively listening in on the communications between your app and your users, and is a prerequisite for HTTP/2 and many new web platform APIs. Learn more.

Browsers can proactively prompt users to add your app to their homescreen, which can lead to higher engagement. Learn more. Failures: No manifest was fetched.

Screen reader users rely on frame titles to describe the contents of frames. Learn more.

If a page doesn't specify a lang attribute, a screen reader assumes that the page is in the default language that the user chose when setting up the screen reader. If the page isn't actually in the default language, then the screen reader might not announce the page's text correctly. Learn more.