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

This is the largest contentful element painted within the viewport

Consider using `<link rel=preload>` to prioritize fetching resources that are currently requested later in page load

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

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

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

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

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

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

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

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 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

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

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

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

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

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

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

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/).

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

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

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

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

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

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

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)

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

Consider using `<link rel=preload>` to prioritize fetching resources that are currently requested later in page load

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

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

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

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

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

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

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

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

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

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

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

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

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