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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

Animations which are not composited can be janky and increase CLS

This is the largest contentful element painted within the viewport

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Descriptive link text helps search engines understand your content

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

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

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

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

Animations which are not composited can be janky and increase CLS

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

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)

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

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

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

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

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

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

Descriptive link text helps search engines understand your content

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

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

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

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

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

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

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

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

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

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

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

This is the largest contentful element painted within the viewport

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