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

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

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

Descriptive link text helps search engines understand your content

This is the largest contentful element painted within the viewport

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

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

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

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

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

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

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

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

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/).

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

Minifying JavaScript files can reduce payload sizes and script parse time

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

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

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

Minifying CSS files can reduce network payload sizes

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

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

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

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

The Critical Request Chains below show you what resources are loaded with a high priority. Consider reducing the length of chains, reducing the download size of resources, or deferring the download of unnecessary resources to improve page load

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

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)

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

Remove unused JavaScript to reduce bytes consumed by network activity

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

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

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

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

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

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

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

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

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

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

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

The Critical Request Chains below show you what resources are loaded with a high priority. Consider reducing the length of chains, reducing the download size of resources, or deferring the download of unnecessary resources to improve page load

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

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

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

Minifying JavaScript files can reduce payload sizes and script parse time

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

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

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

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

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

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

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)

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/).

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

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

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

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

Descriptive link text helps search engines understand your content

Minifying CSS files can reduce network payload sizes

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

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

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

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

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

Remove unused JavaScript to reduce bytes consumed by network activity

This is the largest contentful element painted within the viewport

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