Tests

All sites should be protected with HTTPS, even ones that don’t handle sensitive data. This includes avoiding 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. Learn more.

If you’ve already set up HTTPS, make sure that you redirect all HTTP traffic to HTTPS in order to enable secure web features for all your users. Learn more.

The 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. Learn more.

Add a <meta name="viewport"> tag to optimize your app for mobile screens. Learn more.

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

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

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

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

This is what the load of your site looked like.

The last screenshot captured of the pageload.

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. Learn more.

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

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

Cumulative Layout Shift measures the movement of visible elements within the viewport. Learn more.

Errors logged to the console indicate unresolved problems. They can come from network request failures and other browser concerns. Learn more

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

First CPU Idle marks the first time at which the page’s main thread is quiet enough to handle input. Learn more.

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

Consider instrumenting your app with the User Timing API to measure your app’s real-world performance during key user experiences. Learn more.

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. Learn more.

Redirects introduce additional delays before the page can be loaded. Learn more.

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. Learn more.

For ideal appearance on iOS when users add a progressive web app to the home screen, define an apple-touch-icon. It must point to a non-transparent 192px (or 180px) square PNG. Learn More.

A themed splash screen ensures a high-quality experience when users launch your app from their homescreens. Learn more.

The browser address bar can be themed to match your site. Learn more.

A maskable icon ensures that the image fills the entire shape without being letterboxed when installing the app on a device. Learn more.

If the width of your app’s content doesn’t match the width of the viewport, your app might not be optimized for mobile screens. Learn more.

Image display dimensions should match natural aspect ratio. Learn more.

Image natural dimensions should be proportional to the display size and the pixel ratio to maximize image clarity. Learn more.

Preload optional fonts so first-time visitors may use them. Learn more

Deprecated APIs will eventually be removed from the browser. Learn more.

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

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

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

Consider adding preconnect or dns-prefetch resource hints to establish early connections to important third-party origins. Learn more.

Leverage the font-display CSS feature to ensure text is user-visible while webfonts are loading. Learn more.

Collection of useful page vitals.

Lists the network requests that were made during page load.

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. Learn more.

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. Learn more.

Lists the toplevel main thread tasks that executed during page load.

Collects all available metrics.

Keep the quantity and size of network requests under the targets set by the provided performance budget. Learn more.

Set a timing budget to help you keep an eye on the performance of your site. Performant sites load fast and respond to user input events quickly. Learn more.

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

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. Learn more.

Some third-party embeds can be lazy loaded. Consider replacing them with a facade until they are required. Learn more.

This is the largest contentful element painted within the viewport. Learn More

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

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

The unload event does not fire reliably and listening for it can prevent browser optimizations like the Back-Forward Cache. Consider using the pagehide or visibilitychange events instead. Learn more

Animations which are not composited can be janky and increase CLS. Learn more

Set an explicit width and height on image elements to reduce layout shifts and improve CLS. Learn more

Source maps translate minified code to the original source code. This helps developers debug in production. In addition, Lighthouse is able to provide further insights. Consider deploying source maps to take advantage of these benefits. Learn more.

Preload the image used by the LCP element in order to improve your LCP time. Learn more.

To reach the most number of users, sites should work across every major browser. Learn more.

Transitions should feel snappy as you tap around, even on a slow network. This experience is key to a user’s perception of performance. Learn more.

Ensure individual pages are deep linkable via URL and that URLs are unique for the purpose of shareability on social media. Learn more.

Access keys let users quickly focus a part of the page. For proper navigation, each access key must be unique. Learn more.

Each ARIA role supports a specific subset of aria-* attributes. Mismatching these invalidates the aria-* attributes. Learn more.

When an element doesn’t have an accessible name, screen readers announce it with a generic name, making it unusable for users who rely on screen readers. Learn more.

Assistive technologies, like screen readers, work inconsistently when aria-hidden="true" is set on the document <body>. Learn more.

Focusable descendents within an [aria-hidden="true"] element prevent those interactive elements from being available to users of assistive technologies like screen readers. Learn more.

When an input field doesn’t have an accessible name, screen readers announce it with a generic name, making it unusable for users who rely on screen readers. Learn more.

When an element doesn’t have an accessible name, screen readers announce it with a generic name, making it unusable for users who rely on screen readers. Learn more.

When an element doesn’t have an accessible name, screen readers announce it with a generic name, making it unusable for users who rely on screen readers. Learn more.

Some ARIA roles have required attributes that describe the state of the element to screen readers. Learn more.

Some ARIA parent roles must contain specific child roles to perform their intended accessibility functions. Learn more.

Some ARIA child roles must be contained by specific parent roles to properly perform their intended accessibility functions. Learn more.

ARIA roles must have valid values in order to perform their intended accessibility functions. Learn more.

When a toggle field doesn’t have an accessible name, screen readers announce it with a generic name, making it unusable for users who rely on screen readers. Learn more.

When an element doesn’t have an accessible name, screen readers announce it with a generic name, making it unusable for users who rely on screen readers. Learn more.

When an element doesn’t have an accessible name, screen readers announce it with a generic name, making it unusable for users who rely on screen readers. Learn more.

Assistive technologies, like screen readers, can’t interpret ARIA attributes with invalid values. Learn more.

Assistive technologies, like screen readers, can’t interpret ARIA attributes with invalid names. Learn more.

When a button doesn’t have an accessible name, screen readers announce it as “button”, making it unusable for users who rely on screen readers. Learn more.

Adding ways to bypass repetitive content lets keyboard users navigate the page more efficiently. Learn more.

Low-contrast text is difficult or impossible for many users to read. Learn more.

When definition lists are not properly marked up, screen readers may produce confusing or inaccurate output. Learn more.

Definition list items (<dt> and <dd>) must be wrapped in a parent <dl> element to ensure that screen readers can properly announce them. Learn more.

The title gives screen reader users an overview of the page, and search engine users rely on it heavily to determine if a page is relevant to their search. Learn more.

All focusable elements must have a unique id to ensure that they’re visible to assistive technologies. Learn more.

The value of an ARIA ID must be unique to prevent other instances from being overlooked by assistive technologies. Learn more.

Form fields with multiple labels can be confusingly announced by assistive technologies like screen readers which use either the first, the last, or all of the labels. Learn more.

Screen reader users rely on frame titles to describe the contents of frames. Learn more.

Properly ordered headings that do not skip levels convey the semantic structure of the page, making it easier to navigate and understand when using assistive technologies. Learn more.

If a page doesn’t specify a lang attribute, a screen reader assumes that the page is in the default language that the user chose when setting up the screen reader. If the page isn’t actually in the default language, then the screen reader might not announce the page’s text correctly. Learn more.

Specifying a valid BCP 47 language helps screen readers announce text properly. Learn more.

Informative elements should aim for short, descriptive alternate text. Decorative elements can be ignored with an empty alt attribute. Learn more.

When an image is being used as an <input> button, providing alternative text can help screen reader users understand the purpose of the button. Learn more.

Labels ensure that form controls are announced properly by assistive technologies, like screen readers. Learn more.

Link text (and alternate text for images, when used as links) that is discernible, unique, and focusable improves the navigation experience for screen reader users. Learn more.

Screen readers have a specific way of announcing lists. Ensuring proper list structure aids screen reader output. Learn more.

Screen readers require list items (<li>) to be contained within a parent <ul> or <ol> to be announced properly. Learn more.

Users do not expect a page to refresh automatically, and doing so will move focus back to the top of the page. This may create a frustrating or confusing experience. Learn more.

Disabling zooming is problematic for users with low vision who rely on screen magnification to properly see the contents of a web page. Learn more.

Screen readers cannot translate non-text content. Adding alt text to <object> elements helps screen readers convey meaning to users. Learn more.

A value greater than 0 implies an explicit navigation ordering. Although technically valid, this often creates frustrating experiences for users who rely on assistive technologies. Learn more.

Screen readers have features to make navigating tables easier. Ensuring <td> cells using the [headers] attribute only refer to other cells in the same table may improve the experience for screen reader users. Learn more.

Screen readers have features to make navigating tables easier. Ensuring table headers always refer to some set of cells may improve the experience for screen reader users. Learn more.

Specifying a valid BCP 47 language on elements helps ensure that text is pronounced correctly by a screen reader. Learn more.

When a video provides a caption it is easier for deaf and hearing impaired users to access its information. Learn more.

Custom interactive controls have associated labels, provided by aria-label or aria-labelledby. Learn more.

Custom interactive controls have appropriate ARIA roles. Learn more.

A user can tab into and out of any control or region without accidentally trapping their focus. Learn more.

Custom interactive controls are keyboard focusable and display a focus indicator. Learn more.

Interactive elements, such as links and buttons, should indicate their state and be distinguishable from non-interactive elements. Learn more.

Tabbing through the page follows the visual layout. Users cannot focus elements that are offscreen. Learn more.

If new content, such as a dialog, is added to the page, the user’s focus is directed to it. Learn more.

Offscreen content is hidden with display: none or aria-hidden=true. Learn more.

Landmark elements (<main>, <nav>, etc.) are used to improve the keyboard navigation of the page for assistive technology. Learn more.

DOM order matches the visual order, improving navigation for assistive technology. Learn more.

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

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

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

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

Minifying CSS files can reduce network payload sizes. Learn more.

Minifying JavaScript files can reduce payload sizes and script parse time. Learn more.

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

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

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. Learn more.

Optimized images load faster and consume less cellular data. Learn more.

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

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

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. Learn more

Remove large, duplicate JavaScript modules from bundles to reduce unnecessary 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. Learn More

Application Cache is deprecated. Learn more.

Specifying a doctype prevents the browser from switching to quirks-mode. Learn more.

A character encoding declaration is required. It can be done with a <meta> tag in the first 1024 bytes of the HTML or in the Content-Type HTTP response header. Learn more.

A large DOM will increase memory usage, cause longer style calculations, and produce costly layout reflows. Learn more.

Add rel="noopener" or rel="noreferrer" to any external links to improve performance and prevent security vulnerabilities. Learn more.

Users are mistrustful of or confused by sites that request their location without context. Consider tying the request to a user action instead. Learn more.

Issues logged to the Issues panel in Chrome Devtools indicate unresolved problems. They can come from network request failures, insufficient security controls, and other browser concerns. Open up the Issues panel in Chrome DevTools for more details on each issue.

For users on slow connections, external scripts dynamically injected via document.write() can delay page load by tens of seconds. Learn more.

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

All front-end JavaScript libraries detected on the page. Learn more.

Users are mistrustful of or confused by sites that request to send notifications without context. Consider tying the request to user gestures instead. Learn more.

Preventing password pasting undermines good security policy. Learn more.

Consider marking your touch and wheel event listeners as passive to improve your page’s scroll performance. Learn more.

Meta descriptions may be included in search results to concisely summarize page content. Learn more.

Pages with unsuccessful HTTP status codes may not be indexed properly. Learn more.

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. Learn more.

Descriptive link text helps search engines understand your content. Learn more.

Search engines may use href attributes on links to crawl websites. Ensure that the href attribute of anchor elements links to an appropriate destination, so more pages of the site can be discovered. Learn More

Search engines are unable to include your pages in search results if they don’t have permission to crawl them. Learn more.

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

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. Learn more.

hreflang links tell search engines what version of a page they should list in search results for a given language or region. Learn more.

Search engines can’t index plugin content, and many devices restrict plugins or don’t support them. Learn more.

Canonical links suggest which URL to show in search results. Learn more.

Run the Structured Data Testing Tool and the Structured Data Linter to validate structured data. Learn more.