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

This is the largest contentful element painted within the viewport. Learn more about the Largest Contentful Paint element

Reduce unused rules from stylesheets and defer CSS not used for above-the-fold content to decrease bytes consumed by network activity. Learn how to reduce unused CSS.

Image formats like WebP and AVIF often provide better compression than PNG or JPEG, which means faster downloads and less data consumption. Learn more about modern image formats.

Optimized images load faster and consume less cellular data. Learn how to efficiently encode images.

A long cache lifetime can speed up repeat visits to your page. Learn more about efficient cache policies.

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

Set an explicit width and height on image elements to reduce layout shifts and improve CLS. Learn how to set image dimensions

The maximum potential First Input Delay that your users could experience is the duration of the longest task. Learn more about the Maximum Potential First Input Delay metric.

Deprecated APIs will eventually be removed from the browser. Learn more about deprecated APIs.

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 served over 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 about HTTPS.

Make sure that you redirect all HTTP traffic to HTTPS in order to enable secure web features for all your users. Learn more.

Image natural dimensions should be proportional to the display size and the pixel ratio to maximize image clarity. Learn how to provide responsive images.

Properly ordered headings that do not skip levels convey the semantic structure of the page, making it easier to navigate and understand when using assistive technologies. Learn more about heading order.

Disabling zooming is problematic for users with low vision who rely on screen magnification to properly see the contents of a web page. Learn more about the viewport meta tag.

Low-contrast text is difficult or impossible for many users to read. Learn how to provide sufficient color contrast.