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MDN Web Docs @developer.mozilla.org · 44m

📣 Firefox 144 is out!

What's new for developers:
🧩 View Transition API for SPAs
⚙️ New Map/WeakMap methods (getOrInsert)
🧱 Element.moveBefore()
📱 ScreenOrientation.lock()
🕐 Built-in time picker for (🧪exp.)

Read more 👇
developer.mozilla.org/en-US/docs/...

Firefox 144 for developers - Mozilla | MDN

This article provides information about the changes in Firefox 144 that affect developers. Firefox 144 was released on October 14, 2025.

developer.mozilla.org

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MDN Web Docs @developer.mozilla.org · 10h

✨ Imagine if your site could animate smoothly between pages — without a reload.

That’s now possible with CSS View Transitions, bringing SPA-like animations to multi-page apps!

A beginner-friendly guide by Yash Raj Bharti ↓
developer.mozilla.org/en-US/blog/...

A beginner-friendly guide to view transitions in CSS | MDN Blog

Learn how to bring smooth, animated navigation to multi-page apps with view transitions. With just one line of CSS, you can enable seamless transitions between pages.

developer.mozilla.org

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MDN Web Docs @developer.mozilla.org · 14h

Make MDN shine brighter for you! 🔆

Join our quick survey to share how MDN fits into your daily coding and learning routine.

⏱️ Just 10 minutes
✅ Skip questions if you like
🔒 Your privacy is our priority

Dive into the survey now 📝
survey.alchemer.com/s3/8409929/...

survey.alchemer.com

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Reposted by MDN Web Docs

Jake Archibald @jakearchibald.com · 17h

I dug into progressive image rendering and found a bunch of common assumptions aren't quite true.

➡️ JPEG & WebP progressive-renders worse in Safari
➡️ AVIF _does_ support progressive
➡️ But JPEG XL in Safari doesn't
➡️ JPEG XL decodes much slower than AVIF
⬇️ and more

jakearchibald.com/2025/present...

The present and potential future of progressive image rendering

Exploring progressive image rendering across JPEG, PNG, WebP, AVIF, and JPEG XL.

jakearchibald.com

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MDN Web Docs @developer.mozilla.org · 9d

Thank you so much! 🙌

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MDN Web Docs @developer.mozilla.org · 9d

Help us make MDN even better for you! 📣

We’re running a short survey to understand how developers use MDN in their day-to-day work and learning.

⏱️ Takes ~10 minutes
✅ All questions optional
🔒 Responses are anonymous

Take the survey 📝
survey.alchemer.com/s3/8409929/...

survey.alchemer.com

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MDN Web Docs @developer.mozilla.org · 10d

📷 Ever wonder what’s really happening behind your web images?

From pixels to formats to compression, you should use:
- JPEG for details
- PNG for transparency
- WebP & AVIF for web-performance
- SVG for resolution-independent graphics

Read more 👇
developer.mozilla.org/en-US/blog/...

Pixel data from encoders to decoders | MDN Blog

From individual pixels to fully decoded images on your screen, raw pixel data gets transformed, compressed, and efficiently delivered. Learn about the techniques and optimizations that shrink image information without any perceivable loss in quality.

developer.mozilla.org

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MDN Web Docs @developer.mozilla.org · 13d

Margin? Border? Padding? Content? 💅

The CSS box model is the foundation of layout, and MDN’s interactive exercises help you truly understand how it all fits together.

💡 Practice live in your browser
developer.mozilla.org/en-US/docs/...

Test your skills: The box model - Learn web development | MDN

The aim of this skill test is to help you assess whether you understand the CSS box model.

developer.mozilla.org

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MDN Web Docs @developer.mozilla.org · 15d

🕵️‍♂️ The User-Agent HTTP header tells the server what client is making the request, like browser, OS, and rendering engine.

It helps servers:
✅ Serve browser-specific content
✅ Log usage patterns
❌ But can also be a source of fingerprinting

Read more 👇
developer.mozilla.org/en-US/docs/...

User-Agent header - HTTP | MDN

The HTTP User-Agent request header is a characteristic string that lets servers and network peers identify the application, operating system, vendor, and/or version of the requesting user agent.

developer.mozilla.org

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MDN Web Docs @developer.mozilla.org · 20d

Style text selections with ::highlight!

The ::highlight pseudo-element lets you customize how text highlights appear. Not just for user selection (::selection), but also for custom highlights created via the Highlight API

Learn more 👇
developer.mozilla.org/en-US/docs/...

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MDN Web Docs @developer.mozilla.org · 21d

Tired of long-running scripts blocking the UI?

The Web Workers API lets you run JS in the background, keeping your app responsive and smooth.
✅ Offload heavy tasks
✅ Keep the main thread free
✅ Great for data crunching, parsing, and more

Read how 👇
developer.mozilla.org/en-US/docs/...

Using Web Workers - Web APIs | MDN

Web Workers are a simple means for web content to run scripts in background threads. The worker thread can perform tasks without interfering with the user interface. In addition, they can make network requests using the fetch() or XMLHttpRequest APIs. Once created, a worker can send messages to the JavaScript code that created it by posting messages to an event handler specified by that code (and vice versa).

developer.mozilla.org

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MDN Web Docs @developer.mozilla.org · 22d

🕵️‍♂️ The User-Agent HTTP header tells the server what client is making the request, like browser, OS, and rendering engine.

It helps servers:
✅ Serve browser-specific content
✅ Log usage patterns
❌ But can also be a source of fingerprinting

Read more 👇
developer.mozilla.org/en-US/docs/...

User-Agent header - HTTP | MDN

The HTTP User-Agent request header is a characteristic string that lets servers and network peers identify the application, operating system, vendor, and/or version of the requesting user agent.

developer.mozilla.org

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MDN Web Docs @developer.mozilla.org · 23d

What does the k1 attribute do in SVG? 🌀

The k1 attribute is used with the filter element in SVG to apply convolution effects. It’s part of the kernel matrix that defines how pixels are transformed.

Learn more 👇
developer.mozilla.org/en-US/docs/...

k1 - SVG | MDN

The k1 attribute defines one of the values to be used within the arithmetic operation of the <feComposite> filter primitive.

developer.mozilla.org

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MDN Web Docs @developer.mozilla.org · 24d

🧪 Thinking of using fetch() streams to track upload/download progress?

@jakearchibald.com shares more, and how could limit future browser optimizations.

✅ Streams = Great for parallel processing
❌ Streams ≠ Reliable for measuring up/down %

Read more 👇
jakearchibald.com/2025/fetch-...

Fetch streams are great, but not for measuring upload/download progress

They're inaccurate, and there are better ways.

jakearchibald.com

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Reposted by MDN Web Docs

Firefox Nightly @firefoxnightly.bsky.social · 24d

[Nightly Blog] Webcam previews and more! – These Weeks in Firefox: Issue 187 blog.nightly.mozilla.org/2025/09/12/w...

Webcam previews and more! – These Weeks in Firefox: Issue 187 – Firefox Nightly News

Highlights Nicolas Chevobbe added presentational hints in the Inspector's rule-view (#1212289)

blog.nightly.mozilla.org

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MDN Web Docs @developer.mozilla.org · 24d

Guide assistive tech with aria-orientation 🧭

The aria-orientation attribute helps screen readers and other assistive tech understand how a UI component is laid out, horizontal or vertical, with widgets like
↕️ Sliders
↔️ Tabs
🔼 Treeviews

Read more 👇
developer.mozilla.org/en-US/docs/...

ARIA: aria-orientation attribute - ARIA | MDN

The aria-orientation attribute indicates whether the element's orientation is horizontal, vertical, or unknown/ambiguous.

developer.mozilla.org

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MDN Web Docs @developer.mozilla.org · 27d

Tired of hacking together deep copies with JSON.parse(JSON.stringify(...))? 🔁

The structuredClone() method lets you safely clone complex JavaScript objects.
No data loss. No surprises. Just clean, reliable cloning.

Learn more 👇
developer.mozilla.org/en-US/docs/...

Window: structuredClone() method - Web APIs | MDN

The structuredClone() method of the Window interface creates a deep clone of a given value using the structured clone algorithm.

developer.mozilla.org

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MDN Web Docs @developer.mozilla.org · 27d

We’d love your feedback! 📣

Take our quick 1–2 minute survey on using ReadableStream as a request body with the Fetch API.

Your input helps shape browser support and prioritize real-world use cases.

Share your thoughts 📝
survey.alchemer.com/s3/8460326/...

survey.alchemer.com

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Reposted by MDN Web Docs

Mozilla @mozilla.org · Sep 12

🚨 Schedule drop 🚨
Mozilla Festival 2025 is live: 240+ sessions, film fest, youth-led forums, tech + art.
📅 Nov 7–9 | Barcelona
Join us: bit.ly/3K6gmqx
#MozFest

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Reposted by MDN Web Docs

Jake Archibald @jakearchibald.com · Sep 15

📝 Fetch streams are great, but contrary to popular belief, they're not good for measuring upload/downloading progress.

⬇️ Here's why, and how to avoid the gotchas ⬇️

jakearchibald.com/2025/fetch-s...

Fetch streams are great, but not for measuring upload/downloading progress

They're inaccurate, and there are better ways.

jakearchibald.com

4 17 150

Reposted by MDN Web Docs

Firefox Nightly @firefoxnightly.bsky.social · Sep 16

Mozilla - Ask a Fox event
community.mozilla.org/campaigns/as...

Mozilla - Ask a Fox event - Mozilla Community Portal

The Mozilla Support platform (a.k.a. SUMO) receives over 20 million visits each month. It’s the go-to place for Firefox users to

community.mozilla.org

1 6

Reposted by MDN Web Docs

Pranshu Khanna @pran.sh · Sep 16

Have thoughts on using ReadableStream as a request body in fetch()?

We're running a quick survey (1–2 mins) to gauge interest, it'll help shape what browser folks prioritize next.

If you care about streaming uploads or fetch, this is for you 👇
survey.alchemer.com/s3/8460326/...

survey.alchemer.com

1 3

Reposted by MDN Web Docs

mozilla.ai @mozilla.ai · 29d

We're excited to announce that our ML Systems Engineer Raz Besaleli, and Head of AI Engineering Irina Vidal Migallón will speak at the DataFest Tbilisi (Nov 27–29)!

Raz on lessons from systems engineering for resilient AI, and Irina on key risks when working with AI.

More info: www.datafest.ge

DataFest Tbilisi 2025

www.datafest.ge

1 3

Reposted by MDN Web Docs

Firefox @firefox.com · 29d

Firefox 143 is here, check out what's new:

✔️ Drag tabs to pin them. Simple, effective.
✔️ Camera preview in permission dialog. No more guesswork.
✔️ Stronger Fingerprinting Protection.
✔️ Smarter Private Browsing downloads (decide to keep or auto-delete).

www.firefox.com/en-US/firefo...

Firefox 143.0, See All New Features, Updates and Fixes

www.firefox.com

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Reposted by MDN Web Docs

Mozilla @mozilla.org · 29d

Last chance to apply ⚡

Mozilla @mozilla.org · Sep 11

Applications are now open for our Creative Futures Counterstructures Residency✨

This 10-week cultural residency is for artists + technologists looking to re-imagine and prototype the possibilities of ethical AI systems.

San Francisco📍
Apply by Sept 17✨
www.mozillafoundation.org/en/creative-...

Creative Futures Counterstructures | Mozilla Foundation

Creative Futures Counterstructures (CFC) is Mozilla Foundation’s 10-week cultural R&D residency where creative technologists and communities come together to imagine, test, and build alternative tech ...

www.mozillafoundation.org

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