Some third-party scripts may contain known security vulnerabilities that are easily identified and exploited by attackers

This is the largest contentful element painted within the viewport

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

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

Redirects introduce additional delays before the page can be loaded

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

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

First CPU Idle marks the first time at which the page's main thread is quiet enough to handle input. [Learn more](https://web.dev/first-cpu-idle/).

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

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

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

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

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

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

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

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

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

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

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

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)

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

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 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

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

Large JavaScript libraries can lead to poor performance. Prefer smaller, functionally equivalent libraries to reduce your bundle size

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

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

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

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

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

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

Remove unused JavaScript to reduce bytes consumed by network activity

Estimated Input Latency is an estimate of how long your app takes to respond to user input, in milliseconds, during the busiest 5s window of page load. If your latency is higher than 50 ms, users may perceive your app as laggy

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

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

Minifying JavaScript files can reduce payload sizes and script parse time

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

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

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

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

First CPU Idle marks the first time at which the page's main thread is quiet enough to handle input. [Learn more](https://web.dev/first-cpu-idle/).

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

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

First Contentful Paint 3G marks the time at which the first text or image is painted while on a 3G network

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

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

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

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

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

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

Large JavaScript libraries can lead to poor performance. Prefer smaller, functionally equivalent libraries to reduce your bundle size

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

Redirects introduce additional delays before the page can be loaded

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

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

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

Remove unused JavaScript to reduce bytes consumed by network activity

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

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

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

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

Some third-party scripts may contain known security vulnerabilities that are easily identified and exploited by attackers

Estimated Input Latency is an estimate of how long your app takes to respond to user input, in milliseconds, during the busiest 5s window of page load. If your latency is higher than 50 ms, users may perceive your app as laggy

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 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

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

This is the largest contentful element painted within the viewport

Minifying JavaScript files can reduce payload sizes and script parse time

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

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

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)

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