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

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

If your robots.txt file is malformed, crawlers may not be able to understand how you want your website to be crawled or indexed

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

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

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

Minifying CSS files can reduce network payload sizes

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

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

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

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

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

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)

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

Optimized images load faster and consume less cellular data

This is the largest contentful element painted within the viewport

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

Image formats like WebP and AVIF often provide better compression than PNG or JPEG, which means faster downloads and less data consumption

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

Minifying JavaScript files can reduce payload sizes and script parse time

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

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

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

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

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

Redirects introduce additional delays before the page can be loaded

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

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

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

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

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

If your robots.txt file is malformed, crawlers may not be able to understand how you want your website to be crawled or indexed

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

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

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

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

Image formats like WebP and AVIF often provide better compression than PNG or JPEG, which means faster downloads and less data consumption

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

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

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

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

Minifying JavaScript files can reduce payload sizes and script parse time

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

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

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

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)

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

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

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

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

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

Optimized images load faster and consume less cellular data

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

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

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

Redirects introduce additional delays before the page can be loaded

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

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

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

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

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

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

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

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