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

This is the largest contentful element painted within the viewport

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

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

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

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

Animations which are not composited can be janky and increase CLS

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

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

Redirects introduce additional delays before the page can be loaded

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

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

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

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

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

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

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

Minifying CSS files can reduce network payload sizes

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

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

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

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

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)

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

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

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

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

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

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

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

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

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

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

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

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

Redirects introduce additional delays before the page can be loaded

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

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

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

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

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

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

This is the largest contentful element painted within the viewport

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

Animations which are not composited can be janky and increase CLS

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

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

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

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

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

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

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

Minifying CSS files can reduce network payload sizes

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

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

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

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

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

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