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

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

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

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

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

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

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

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

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

This is the largest contentful element painted 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

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

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

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

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

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

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

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

Minifying JavaScript files can reduce payload sizes and script parse time

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/).

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

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

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

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

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

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

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

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

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

Minifying JavaScript files can reduce payload sizes and script parse time

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

This is the largest contentful element painted within the viewport

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

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

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

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

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

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

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

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

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/).

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

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

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

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