@MozDevNet

The official MDN Web Docs account. We deliver the best web docs around.

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developer.mozilla.org
Joined March 2013
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🆕 Customize MDN's browser compat tables! Press ⚙️ Settings on any compat table to choose which browsers and engines you see, and hide the ones you don't need. Your picks are saved in your browser. Try it 👇 developer.mozilla.org/en-US/…
MDN's browser compatibility table for the HTML popover attribute. Its columns cover desktop and mobile browsers, showing which versions support the attribute and its "hint" value. A "Settings" button sits above the table.

ALT MDN's browser compatibility table for the HTML popover attribute. Its columns cover desktop and mobile browsers, showing which versions support the attribute and its "hint" value. A "Settings" button sits above the table.

The Browser compatibility settings dialog on MDN. Browsers appear as chips grouped under Desktop, Mobile, Server and XR, and each one can be added to or removed from the table.

ALT The Browser compatibility settings dialog on MDN. Browsers appear as chips grouped under Desktop, Mobile, Server and XR, and each one can be added to or removed from the table.

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🆕 Introducing the MDN MCP server! Bring MDN's docs and browser compat data straight into your AI agent or IDE for accurate, up-to-date answers about the web platform. No more outdated guesses from training data. Learn more 👇 developer.mozilla.org/en-US/…
A headline Introducing MDN MCP server above a terminal window titled Light-dark CSS function for images, showing a prompt asking how to use the light-dark() CSS function for images and which browsers support it, with a note that the mdn tool was called 4 times, followed by an answer explaining that light-dark() takes two image values and works anywhere an image is accepted. The MDN logo appears on the right.

ALT A headline Introducing MDN MCP server above a terminal window titled Light-dark CSS function for images, showing a prompt asking how to use the light-dark() CSS function for images and which browsers support it, with a note that the mdn tool was called 4 times, followed by an answer explaining that light-dark() takes two image values and works anywhere an image is accepted. The MDN logo appears on the right.

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Ever wish HTTP status codes were easier to remember? 🖼️ Check out this MDN cheatsheet that pairs each status code with an emoji to help you visualize what each one means, from 200 OK ✅ to 418 I’m a teapot 🫖 Check it out 👇
A colorful infographic titled “MDN HTTP Code Cheatsheet with Emojis.” It categorizes HTTP status codes using emoji-enhanced lists grouped by status code classes.

ALT A colorful infographic titled “MDN HTTP Code Cheatsheet with Emojis.” It categorizes HTTP status codes using emoji-enhanced lists grouped by status code classes.

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🦊 Firefox 150: web extensions can now use the Web Authentication API. Extensions can create and retrieve WebAuthn credentials for any domain covered by their host permissions. Read Now 👇 developer.mozilla.org/en-US/…
Firefox 150 release notes feature a minimalist design with soft colors, highlighting new capabilities for web extensions.

ALT Firefox 150 release notes feature a minimalist design with soft colors, highlighting new capabilities for web extensions.

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🦊 New in Firefox 150: the revert-rule CSS keyword. Make a property behave as if the current rule didn't exist, letting a value from another matching rule take effect instead. Read Now 👇 developer.mozilla.org/en-US/…
Firefox 150 release notes with a smooth background design featuring soft waves in pastel colors.

ALT Firefox 150 release notes with a smooth background design featuring soft waves in pastel colors.

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🦊 Firefox 150: light-dark() now accepts image values — not just colors. Use it with images and gradients to adapt visuals based on color scheme. background: light-dark(url(light.png), url(dark.png)); Read Now 👇 developer.mozilla.org/en-US/…
Firefox 150 release notes feature a pastel background with waves, emphasizing updates and new features.

ALT Firefox 150 release notes feature a pastel background with waves, emphasizing updates and new features.

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🦊 Firefox 150 ships ariaNotify() on Document and Element. Queue text to be announced by a screen reader — a more ergonomic and reliable alternative to ARIA live regions. Read Now 👇 developer.mozilla.org/en-US/…
Firefox 150 release notes highlighted with a light background and wavy design, inviting users to read more.

ALT Firefox 150 release notes highlighted with a light background and wavy design, inviting users to read more.

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🦊 Firefox 150: color-mix() now accepts more than two colors at once. Mix any number of colors in a single declaration — no more nesting multiple calls. Read Now 👇 developer.mozilla.org/en-US/…
Firefox 150 release notes feature a pastel background with wavy patterns, highlighting the new color-mix() function for CSS.

ALT Firefox 150 release notes feature a pastel background with wavy patterns, highlighting the new color-mix() function for CSS.

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🦊 Firefox 150: <img sizes="auto"> is now supported. Lazy-loaded images use their calculated layout size to select from srcset — no more duplicating media queries in HTML. Read Now 👇 developer.mozilla.org/en-US/…
Firefox 150 release notes feature a soft pastel background with text highlighting updates and a call to action to read more.

ALT Firefox 150 release notes feature a soft pastel background with text highlighting updates and a call to action to read more.

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Have you heard of CSS Subgrid? 🤔 A grid item can now pass its parent's grid lines to children, so nested elements align perfectly with the outer layout. No more hacky workarounds for aligned nested grids. Learn more 👇 developer.mozilla.org/en-US/…
Code snippet showcasing CSS Subgrid implementation with defined grid properties for a main grid, items, and sub-items.

ALT Code snippet showcasing CSS Subgrid implementation with defined grid properties for a main grid, items, and sub-items.

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Firefox 150 ships 7 media pseudo-classes: :buffering, :muted, :paused, :playing, :seeking, :stalled, :volume-locked. Style <audio> and <video> elements based on their playback state. Read Now 👇 developer.mozilla.org/en-US/…
Firefox 150 release notes feature a light background with pastel waves. Includes a clear call to action to read more about updates.

ALT Firefox 150 release notes feature a light background with pastel waves. Includes a clear call to action to read more about updates.

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🆕 The URL Pattern API is Newly Available! Use it to match and extract parts of URLs, no need to reinvent routing logic. Supports literals, wildcards, named groups, and even regex constraints. Learn how it works 👇 developer.mozilla.org/en-US/…
Dark-themed code snippet showing URLPattern examples on MDN: two JavaScript blocks matching "/books" and "/books/:id" with console.log outputs.

ALT Dark-themed code snippet showing URLPattern examples on MDN: two JavaScript blocks matching "/books" and "/books/:id" with console.log outputs.

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Wait for all promises, even the failing ones 🔄 `Promise.allSettled()` waits for every promise to finish, success or failure. ⋅ Returns { status: 'fulfilled', value } or { status: 'rejected', reason } ⋅ Perfect for batch operations Learn more 👇 developer.mozilla.org/en-US/…
JavaScript code demonstrating `Promise.allSettled()` handling fulfilled and rejected promises, along with results logging output.

ALT JavaScript code demonstrating `Promise.allSettled()` handling fulfilled and rejected promises, along with results logging output.

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