Service worker is the technology that enables your app to use many Progressive Web App features, such as offline, add to homescreen, and push notifications. With proper service worker and manifest implementations, browsers can proactively prompt users to add your app to their homescreen, which can lead to higher engagement

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

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

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

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

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

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.

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

Descriptive link text helps search engines understand your content

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 served over 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

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

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

Remove unused JavaScript to reduce bytes consumed by network activity

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

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

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

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/).

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

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

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

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

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

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

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

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

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

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

Service worker is the technology that enables your app to use many Progressive Web App features, such as offline, add to homescreen, and push notifications. With proper service worker and manifest implementations, browsers can proactively prompt users to add your app to their homescreen, which can lead to higher engagement

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

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

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

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

Descriptive link text helps search engines understand your content

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

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

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

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

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

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

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 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

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

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

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

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

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

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

Remove unused JavaScript to reduce bytes consumed by network activity

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

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 served over 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

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