These DOM elements contribute most to the CLS of the page

Reduce unused JavaScript and defer loading scripts until they are required to decrease bytes consumed by network activity

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. With proper service worker and manifest implementations, browsers can proactively prompt users to add your app to their homescreen, which can lead to higher engagement

A large DOM will 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/articles/reflow)

Large network payloads cost users real money and are highly correlated with long load times

First Meaningful Paint measures when the primary content of a page is visible

Sum of all time periods between FCP and Time to Interactive, when task length exceeded 50ms, expressed in milliseconds

All sites should be protected with HTTPS, even ones that don't handle sensitive data. This includes avoiding [mixed content](https://developers.google.com/web/fundamentals/security/prevent-mixed-content/what-is-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

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

Largest Contentful Paint marks the time at which the largest text or image is painted

A long cache lifetime can speed up repeat visits to your page

The maximum potential First Input Delay that your users could experience is the duration of the longest task

Time to Interactive is the amount of time it takes for the page to become fully interactive

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

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

Server latencies can impact web performance. If the server latency of an origin is high, it's an indication the server is overloaded or has poor backend performance

Image formats like WebP and AVIF often provide better compression than PNG or JPEG, which means faster downloads and less data consumption

Cumulative Layout Shift measures the movement of visible elements within the viewport

This is the largest contentful element painted within the viewport

Speed Index shows how quickly the contents of a page are visibly populated

First Contentful Paint marks the time at which the first text or image is painted

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

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

Network round trip times (RTT) have a large impact on performance. If the RTT to an origin is high, it's an indication that servers closer to the user could improve performance

Keep the server response time for the main document short because all other requests depend on it

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

Server latencies can impact web performance. If the server latency of an origin is high, it's an indication the server is overloaded or has poor backend performance

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

Keep the server response time for the main document short because all other requests depend on it

A large DOM will 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/articles/reflow)

Interactive elements like buttons and links should be large enough (48x48px), or have enough space around them, to be easy enough to tap without overlapping onto other elements

These DOM elements contribute most to the CLS of the page

First Meaningful Paint measures when the primary content of a page is visible

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. With proper service worker and manifest implementations, browsers can proactively prompt users to add your app to their homescreen, which can lead to higher engagement

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

Largest Contentful Paint marks the time at which the largest text or image is painted

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

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

The maximum potential First Input Delay that your users could experience is the duration of the longest task

Image formats like WebP and AVIF often provide better compression than PNG or JPEG, which means faster downloads and less data consumption

Network round trip times (RTT) have a large impact on performance. If the RTT to an origin is high, it's an indication that servers closer to the user could improve performance

Large network payloads cost users real money and are highly correlated with long load times

Sum of all time periods between FCP and Time to Interactive, when task length exceeded 50ms, expressed in milliseconds

First Contentful Paint marks the time at which the first text or image is painted

A long cache lifetime can speed up repeat visits to your page

All sites should be protected with HTTPS, even ones that don't handle sensitive data. This includes avoiding [mixed content](https://developers.google.com/web/fundamentals/security/prevent-mixed-content/what-is-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

Time to Interactive is the amount of time it takes for the page to become fully interactive

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

Reduce unused JavaScript and defer loading scripts until they are required to decrease bytes consumed by network activity

This is the largest contentful element painted within the viewport

Speed Index shows how quickly the contents of a page are visibly populated

Cumulative Layout Shift measures the movement of visible elements within the viewport