Firefox 153 Nightly adds JPEG XL, and I’m genuinely pumped

JPEG XL finally shows up in Firefox 153 Nightly, and that alone makes this build worth a staging spin.

Remember when “try a new image format” meant shipping a decoder in your app bundle, praying your CDN kept the right Content-Type, and then watching QA find one broken thumbnail on an old laptop? Now you can start with a browser build and see the whole chain, bytes on the wire, decode time, and how your <picture> fallbacks behave.

Highlights (the stuff you’ll actually notice first)

I’ve watched teams ignore Nightly for months, then scramble when a platform change lands in stable and a tiny assumption breaks checkout. This release feels like the opposite. It hands you a pile of practical wins that you can test in an afternoon.

• JPEG XL support: Serve a .jxl and see if your photo-heavy pages drop transfer size without turning faces into waxy blobs.
• Redesigned Settings page: Less hunting. Cleaner groupings. You can get to the toggle you want without that “wait, which section was it under?” moment.
• QR code sharing from a tab: Right-click a tab, pick Share > Generate QR Code, then print it on a flyer or slap it on a slide deck.
• Built-in PDF upgrades: Add images as new pages, and merge PDFs by dragging in the sidebar. No “open another app” detour.
• DevTools JavaScript Tracer: Turn it on in Settings, then trace function calls when you need to answer, “why did this handler fire 400 times?”
• Extension local file access now asks permission: Firefox stops letting extensions touch local files by default, which should reduce surprise access to your documents.

Deep dive: JPEG XL (what I’d test first)

This is the headline for me. Period.

Early signs look good, but I haven’t stress-tested JPEG XL on a gnarly real-world image pipeline yet, the kind with responsive srcsets, a caching layer that “helpfully” normalizes headers, and a CMS that re-encodes uploads at 2 a.m. If you run anything like that, test it in staging before you get bold.

• Quick win test: Pick one hero photo that currently ships as JPEG. Encode a JPEG XL version. Replace it behind a feature flag and load it in Firefox 153 Nightly.
• What to look at in DevTools: Compare transferred bytes, then zoom the image to 200% and scan edges, hair, and gradients for ringing or smearing.
• Fallback check: Make sure your non-JXL fallback still works. Do not assume every client that hits your CDN will decode JXL.

If your CDN caches by URL only and ignores the Accept header, you can serve the wrong bytes to the wrong browser. Ask me how I know.

Redesigned Settings (small change, real daily payoff)

The thing nobody mentions about Settings redesigns: they either save you 10 seconds a day or they cost your support team three weeks.

Firefox 153 Nightly’s Settings reorg looks like the “save you 10 seconds a day” version. I clicked around looking for common stuff, privacy toggles, search defaults, and the path felt shorter. Some folks hate any UI movement. I get it. I still think this one lands on the right side of the trade.

• How I’d validate it: Pick three common tasks your team actually does, then time them on your current Nightly versus 153.
• What might bite you: Internal docs and screenshots go stale fast. Update them before stable picks this up.

QR code sharing and the “oh, that’s handy” tools

QR code sharing sounds like a gimmick until you need it once, on a deadline, and you do not want yet another website generator in the loop.

Right-click the tab, Share > Generate QR Code, then drop it into printed material. I’ve used this pattern for event check-ins and internal posters, and the difference between “scan this” and “type this URL” shows up instantly in fewer typos and fewer confused people hovering at a registration desk.

• Firefox Labs quick action: Type “labs” or “experiment” in the address bar to jump straight to Firefox Labs.
• Color picker quick action: Type “pick color” or “eyedropper,” click the page, and copy the hex value. Remember when we had to use a separate app for that?

PDF editing that feels like it belongs in a browser

This bit surprised me.

Adding images as new pages inside a PDF sounds basic, but it kills an annoying workflow. You open a PDF, you need to insert a screenshot, you end up exporting, re-importing, re-saving, then someone complains the logo went soft. Firefox just lets you do it where you already are.

• Add images as pages: Open a PDF, use the built-in editor, add an image page, then save a new file.
• Merge PDFs: Drag another PDF into the sidebar to merge documents, useful for stitching reports and receipts.

Developer and platform changes (skim-friendly)

If you build for the web, this release has a fun mix of “finally” and “oh no, I need to run tests.” I like that combination, as long as it stays in staging first.

• WebAssembly JS-Promise-Integration: Nightly notes say it supports the proposal. Treat it as experimental unless Mozilla says otherwise.
• ::-webkit-scrollbar subset: This helps compatibility for sites that shipped WebKit-only scrollbar styling. Keep expectations modest.
• CSS attr() in all properties: Great idea, easy to misuse. Write tests for parsing and fallbacks.
• Updated <select> parsing: This aims at future customizable select behavior. Check form-heavy pages.
• Geolocation icon turns red: Firefox adds a loud visual cue when a site accesses location. I want more of this kind of “you can’t miss it” UX.

Migration notes (how I’d roll this out without drama)

Try it in staging.

Nightly rewards curiosity, but it also punishes careless rollouts. For dev clusters and personal profiles, yolo it on a Friday afternoon. For anything customer-facing, do a tiny canary, watch metrics, then expand.

• JPEG XL rollout: Start with 10 images, not 10,000. Verify Content-Type, verify caching behavior, verify fallbacks.
• Extension local file access: Audit your must-have extensions and confirm which ones now ask permission, then document the new click path for users.
• Web platform changes: Run your automated UI tests on Nightly 153, especially around forms, popovers, and custom CSS.

Other stuff in this release: dependency bumps, a few UI tweaks, the usual. Anyway.