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developer.mozilla.org
Joined March 2013
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πŸ†• Customize MDN's browser compat tables! Press βš™οΈ 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 πŸ‘‡ 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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When and how CSS custom property values are calculated might not be what you expect, and it has a big impact on your styles…
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Major versions of Firefox now land every two weeks, so Firefox 155 dropped today with web platform features including: πŸŽ‰ Fully typed CSS attr() πŸŽ‰ CSS progress() πŸŽ‰ Promise.allKeyed() and allSettledKeyed() πŸŽ‰ Lots of new WebTransport stuff …And more! developer.mozilla.org/en-US/…

Firefox 155 release notes for developers - Mozilla | MDN

This article provides information about the changes in Firefox 155 that affect developers. Firefox 155 was released on September 1, 2026.

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CSS text-box is newly baseline, and it's solves a common text layout issue. Here's how it works: instagram.com/reel/DcORXuGFN…

Firefox for Web Developers (@firefoxwebdevs) β€’ Instagram reel

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Firefox 154 landed today, and brings with it some great web platform features: πŸŽ‰ CSS text-box πŸŽ‰ CSS sibling-index() and sibling-count() πŸŽ‰ JS Iterator methods like chunks, window, includes, & join πŸŽ‰ HTTP No-Vary-Search …And more! developer.mozilla.org/en-US/…

Firefox 154 release notes for developers - Mozilla | MDN

This article provides information about the changes in Firefox 154 that affect developers. Firefox 154 was released on August 18, 2026.

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JS promise integration for WebAssembly landed in Firefox 153, making it easier to work with asynchronous calls from Wasm. Here's how it works:
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JS text imports landed in Firefox 153, making it the first browser to support this feature. Here's how it works:
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Notification actions landed in Firefox 152, allowing you to add quick action buttons to your notifications. Here's how they work:
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CSS field-sizing is newly baseline, meaning you can make various form fields size to their contents, without needing JavaScript.
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Firefox 152 landed today, and includes web platform features like: πŸŽ‰ CSS field-sizing πŸŽ‰ Notification actions πŸŽ‰ unadjustedMovement pointer locks πŸŽ‰ getAnimations() pseudoElement option …and more! developer.mozilla.org/en-US/…

Firefox 152 release notes for developers - Mozilla | MDN

This article provides information about the changes in Firefox 152 that affect developers. Firefox 152 was released on June 16, 2026.

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πŸ†• 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 πŸ‘‡ 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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The Web Serial API landed in Firefox 151, allowing you to connect directly to microcontrollers, dev boards, 3D printers, power meters, and other serial-connected hardware from the web. Here's how it works:
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Ever wish HTTP status codes were easier to remember? πŸ–ΌοΈ Check out this MDN cheatsheet that pairs each status code with an emoji to help you visualize what each one means, from 200 OK βœ… to 418 I’m a teapot πŸ«– Check it out πŸ‘‡
A colorful infographic titled β€œMDN HTTP Code Cheatsheet with Emojis.” It categorizes HTTP status codes using emoji-enhanced lists grouped by status code classes.

ALT A colorful infographic titled β€œMDN 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 πŸ‘‡ 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 πŸ‘‡ 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 β€” 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 πŸ‘‡ 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 β€” a more ergonomic and reliable alternative to ARIA live regions. Read Now πŸ‘‡ 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 β€” no more nesting multiple calls. Read Now πŸ‘‡ 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 β€” no more duplicating media queries in HTML. Read Now πŸ‘‡ 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? πŸ€” 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 πŸ‘‡ 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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