MDN Web Docs @developer.mozilla.org · 25/09/2026🆕 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/docs/W... 27725
MDN Web Docs @developer.mozilla.org · 15/06/2026🆕 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 No more outdated guesses from training data.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/blog/introducing-mdn-mcp-server/ 211823
MDN Web Docs @developer.mozilla.org · 18/05/2026Ever 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 👇 2474
MDN Web Docs @developer.mozilla.org · 18/05/2026🦊 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/docs/... 0292
MDN Web Docs @developer.mozilla.org · 15/05/2026🦊 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/docs/... 0150
MDN Web Docs @developer.mozilla.org · 14/05/2026🦊 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/docs/... 0361
MDN Web Docs @developer.mozilla.org · 13/05/2026🦊 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/docs/... 0321
MDN Web Docs @developer.mozilla.org · 12/05/2026🦊 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/docs/... 0160
MDN Web Docs @developer.mozilla.org · 12/05/2026🦊 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/docs/... 0261
MDN Web Docs @developer.mozilla.org · 11/05/2026Have 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/docs/... 0363
MDN Web Docs @developer.mozilla.org · 11/05/2026🆕 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/docs/... 2736
MDN Web Docs @developer.mozilla.org · 11/05/2026Firefox 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/docs/... 0322
MDN Web Docs @developer.mozilla.org · 10/05/2026Wait 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/docs/... 0352
MDN Web Docs @developer.mozilla.org · 08/05/2026📬 Check own properties safely with Object.hasOwn() A safer alternative to hasOwnProperty, works even on objects with a null prototype. Baseline since 2022 ✅ Learn more 👇 developer.mozilla.org/en-US/docs/... 2463
MDN Web Docs @developer.mozilla.org · 08/05/2026Create frosted glass effects in CSS 🪟 backdrop-filter applies visual effects to the content behind an element - blur, brightness, contrast, and more. backdrop-filter: blur(10px) brightness(0.9); No JavaScript. No canvas tricks. Learn more 👇 developer.mozilla.org/en-US/docs/... 213911
MDN Web Docs @developer.mozilla.org · 08/05/2026The CSS next-sibling combinator (+) selects an element only when it immediately follows another, same parent, no elements between them. img + p { font-weight: bold; } Learn more 👇 developer.mozilla.org/en-US/docs/... 0251
MDN Web Docs @developer.mozilla.org · 07/05/2026🆕 Document.caretPositionFromPoint() is Newly Available! Give it an (x, y) coordinate and get back the exact DOM node and character offset. Perfect for click-to-edit interfaces. Check it out 👇 developer.mozilla.org/en-US/docs/... 0251
MDN Web Docs @developer.mozilla.org · 07/05/2026🆕 The Popover API is Baseline, no JavaScript needed Tooltips, dropdowns, and menus with just HTML attributes. ⋅ popover attribute on any element ⋅ popovertarget to wire the trigger ⋅ Accessible by default, no ARIA hacks Learn more 👇 developer.mozilla.org/en-US/docs/... 01067
MDN Web Docs @developer.mozilla.org · 06/05/2026Better error chaining is finally in JavaScript 🔗 `Error.cause` lets you attach the original error when rethrowing, keeping full context without losing the stack. Learn more 👇 developer.mozilla.org/en-US/docs/... 2711
MDN Web Docs @developer.mozilla.org · 06/05/2026Speed up rendering with content-visibility: auto ⚡ This CSS property skips rendering off-screen content until needed, giving massive performance wins on long pages. ⋅ Pairs with contain-intrinsic-size ⋅ Zero-effort lazy rendering Learn more 👇 developer.mozilla.org/en-US/docs/... 1632
MDN Web Docs @developer.mozilla.org · 05/05/2026React to element size changes, not just the window 📐 `ResizeObserver` fires when any element's dimensions change, perfect for responsive components. ⋅ Observe padding box, content box, or border box ⋅ Works with dynamic DOM changes Learn more 👇 developer.mozilla.org/en-US/docs/... 0241
MDN Web Docs @developer.mozilla.org · 05/05/2026Wait 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/docs/... 0311
MDN Web Docs @developer.mozilla.org · 05/05/2026Run non-critical work without blocking the UI 💤 `requestIdleCallback()` schedules tasks during browser idle time. ⚠️ Limited Availability ⋅ Runs only when the main thread is free ⋅ Great for analytics, prefetching, and cleanup Learn more 👇 developer.mozilla.org/en-US/docs/... 0352
MDN Web Docs @developer.mozilla.org · 04/05/2026JavaScript's date object has been tricky for years, but that is changing. The NEW Temporal API brings, 🌍 Easily handle time zones 📆 Precise date math 🕒 Parse ISO strings without errors ⌛ Durations, date ranges, and more. Start experimenting 👇 developer.mozilla.org/en-US/docs/... 0718
MDN Web Docs @developer.mozilla.org · 01/05/2026JavaScript now has non-mutating array methods ✨ `toSorted()`, `toReversed()`, `toSpliced()`, and `with()` return new arrays instead of modifying the original. No more [...arr].sort() to avoid side effects. Learn more 👇 developer.mozilla.org/en-US/docs/... 819318
MDN Web Docs @developer.mozilla.org · 01/05/2026🆕 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/docs/... 08811
MDN Web Docs @developer.mozilla.org · 30/04/2026Show focus rings only when needed 🎯 :focus-visible applies styles when an element receives focus via keyboard, but not on mouse clicks. Better UX for everyone. Read More 👇 developer.mozilla.org/en-US/docs/... 0384
MDN Web Docs @developer.mozilla.org · 30/04/2026Transform streaming data on the fly 🔄 TransformStream sits between a readable and writable stream, letting you modify chunks as they pass through. Perfect for encoding, compression, or parsing. Learn more 👇 developer.mozilla.org/en-US/docs/... 0211
MDN Web Docs @developer.mozilla.org · 29/04/2026Did you know about Clear-Site-Data header? 👀 One HTTP header to clear cookies, storage, or cache for your site. Perfect for logout flows. Learn more 👇 developer.mozilla.org/en-US/docs/... 011116
MDN Web Docs @developer.mozilla.org · 29/04/2026Schedule work at the right time with queueMicrotask() ⚡ Run a callback after the current task but before rendering. More predictable than setTimeout(fn, 0), lighter than a Promise. Learn more 👇 developer.mozilla.org/en-US/docs/... 0310
MDN Web Docs @developer.mozilla.org · 28/04/2026Format lists like a native speaker 🌐 Intl.ListFormat turns arrays into grammatically correct strings in any locale. Handles "and", "or", and narrow styles automatically. Learn more 👇 developer.mozilla.org/en-US/docs/... 1554
MDN Web Docs @developer.mozilla.org · 28/04/2026Fit images perfectly with object-fit 🖼️ Control how replaced content (images, videos) fills its container. cover, contain, fill, scale-down, or none. No more stretched or squished images. Learn more 👇 developer.mozilla.org/en-US/docs/... 0333
MDN Web Docs @developer.mozilla.org · 27/04/2026Parse and build query strings the easy way 🔗 URLSearchParams gives you a clean API for working with URL parameters. Get, set, append, delete, and iterate, no regex needed. Learn more 👇 developer.mozilla.org/en-US/docs/... 0253
MDN Web Docs @developer.mozilla.org · 27/04/2026Happening tomorrow at Mozilla Berlin! 🚨 Firefox, open source & the future of the web. 🎤 Firefox Mobile open source contributions 🗺️ Firefox Roadmap & upcoming features 🤝 Networking + raffle 🗓️ Apr 28 // 18:00 RSVP now! 👇 www.meetup.com/berlin-mozi... 0101
MDN Web Docs @developer.mozilla.org · 25/04/2026Mozilla Meetup is back in Berlin! 🥳 🗓️ Apr 28 // 18:00 Firefox, open source & the future of the web. 🎤 Firefox Mobile open source contributions 🗺️ Firefox Roadmap & upcoming features 🤝 Networking + raffle RSVP now! 👇 www.meetup.com/berlin-mozi... 141
MDN Web Docs @developer.mozilla.org · 24/04/2026Transform iterators without converting to arrays 🔄 Iterator helpers like .map(), .filter(), .take(), and .drop() work lazily on any iterable. Process data efficiently without intermediate arrays. Learn more 👇 developer.mozilla.org/en-US/docs/... 0370
MDN Web Docs @developer.mozilla.org · 24/04/2026🦊 Firefox 150 is here! What's new? 🎨 color-mix() accepts multiple colors 🎥 New :playing, :paused, :muted media pseudo-classes 📜 animation-range-start/end for scroll animations ♿ ariaNotify() for screen reader support and more... Release notes 👇 developer.mozilla.org/en-US/docs/... 2240
MDN Web Docs @developer.mozilla.org · 22/04/2026Transform key-value pairs back into objects ↩️ Object.fromEntries() is the inverse of Object.entries(). Convert Maps, arrays, or URLSearchParams directly into plain objects. Learn more 👇 developer.mozilla.org/en-US/docs/... 0400
MDN Web Docs @developer.mozilla.org · 22/04/2026Use gap in flexbox, no more margin hacks 📐 The gap property works in flexbox, grid, and multi-column layouts. Set consistent spacing between items without affecting outer edges. Learn more 👇 developer.mozilla.org/en-US/docs/... 0211
MDN Web Docs @developer.mozilla.org · 21/04/2026Read and build form data with the FormData API 📋 Construct form submissions programmatically, including file uploads. Works with fetch() for modern form handling. Learn more 👇 developer.mozilla.org/en-US/docs/... 0261
MDN Web Docs @developer.mozilla.org · 21/04/2026Control CSS specificity with @layer 🎯 Cascade layers let you define explicit priority between groups of styles. No more !important battles. Learn more 👇 developer.mozilla.org/en-US/docs/... 0284
MDN Web Docs @developer.mozilla.org · 20/04/2026Split text by words and sentences, for any language 🌍 Intl.Segmenter handles locale-aware text segmentation, including CJK languages where spaces don't separate words. Learn more 👇 developer.mozilla.org/en-US/docs/... 2323
MDN Web Docs @developer.mozilla.org · 20/04/2026Write direction-aware CSS with logical properties 🧭 Replace top/right/bottom/left with block-start/inline-end/block-end/inline-start. Your layouts adapt automatically to RTL and vertical writing modes. Learn more 👇 developer.mozilla.org/en-US/docs/... 0211
MDN Web Docs @developer.mozilla.org · 19/04/2026Cancel fetch requests and more with AbortController 🛑 Create a signal, pass it to fetch(), and call abort() when needed. Works with addEventListener, streams, and more. Learn more 👇 developer.mozilla.org/en-US/docs/... 0320
MDN Web Docs @developer.mozilla.org · 19/04/2026Generate cryptographically secure UUIDs in the browser 🔐 `crypto.randomUUID()` is built into the Web Crypto API, no npm package needed. Works in all modern browsers and Node.js 14.17+. Learn more 👇 developer.mozilla.org/en-US/docs/... 6894
MDN Web Docs @developer.mozilla.org · 18/04/2026Search arrays from the end with findLast() 🔍 Array.findLast() and findLastIndex() return the last matching element without reversing the array first. Learn more 👇 developer.mozilla.org/en-US/docs/... 0224
MDN Web Docs @developer.mozilla.org · 18/04/2026Balance your headings automatically ⚖️ text-wrap: balance distributes text evenly across lines, preventing awkward orphan words. Perfect for headlines and short blocks. Learn more 👇 developer.mozilla.org/en-US/docs/... 1342
MDN Web Docs @developer.mozilla.org · 17/04/2026Mix colors directly in CSS 🎨 color-mix() blends two colors in any color space. Create tints, shades, and dynamic palettes without a preprocessor. Learn more 👇 developer.mozilla.org/en-US/docs/... 0301
MDN Web Docs @developer.mozilla.org · 13/04/2026Need to detect when elements enter the viewport? 👀 IntersectionObserver fires a callback when elements cross a visibility threshold. No more scroll event listeners. ⋅ Lazy-load images ⋅ Track ad visibility ⋅ Trigger scroll animations Learn more 👇 developer.mozilla.org/en-US/docs/... 0250
MDN Web Docs @developer.mozilla.org · 13/04/2026If you're in Tokyo on April 15, come hang with the Mozilla community. 🇯🇵 We're hosting a meetup with talks on Firefox, open Q&A, and time to connect with contributors and staff. 📅 April 15 · 18:00–21:00 JST 📍 Downtown Tokyo Limited Spots, register 👇 lu.ma/8gaacap2 071