Firefox 158 Opens the Door to JPEG XL, Smooths Out Scrolling and Patches 77 Security Holes
Mozilla's browser finally learns a modern image format, gets pickier about pixels and quietly slams a lot of doors on attackers.
Ever scrolled a long page on a sharp monitor and felt the text wobble ever so slightly, like it was never quite sure where to land? Firefox 158, which Mozilla pushed out on October 13, 2026, goes after exactly that kind of itch, and it brings a few bigger surprises along for the ride.
A modern image format comes home
The headline addition is support for JPEG XL. The format promises smaller files at the same visual quality as classic JPEG, and until now Firefox simply refused to show it, leaving you to download the file and open it somewhere else. With 158 the browser renders those images directly, which is good news if you browse photography portfolios or image-heavy sites that have started serving the newer format.
Smoother scrolling and a smarter helper
Scroll positions are no longer rounded to whole screen pixels. On high-resolution displays and zoomed pages, that means movement feels more fluid and text sits exactly where it should. Another welcome tweak lands in the New Tab page: your custom backgrounds now live in a library called "Your images", so the last picture you picked is no longer the only one you can return to.
Smart Window also learns a new trick. Click into a form field, or choose "Fill" under Sources, and Firefox suggests entries drawn from your open tabs and saved autofill data, which takes some of the pain out of long registration forms. Translation grows too, with Albanian, Belarusian and Filipino joining the supported languages.
Windows details that matter
Windows users with high-contrast themes get real attention this time. Menus such as List All Tabs, Settings and the unified search menu now follow your custom contrast colors, so they stay readable instead of fading into the background. The first letter of each search engine name in the search button menu is also no longer underlined, an oddity that could clash with keyboard shortcuts. A crash while loading favicons has been squashed as well.
The security side
Mozilla patched up to 77 vulnerabilities across the 158, 153.5 ESR and 115.43.0 ESR lines, and rates 30 of them as High. The full details sit in Mozilla's security advisories, but the number alone tells you this is not an update to postpone.
Our verdict
Update today. The new features are pleasant, yet the sheer size of the security batch is the real reason: a browser touches everything you do online, and this release closes an unusually large number of gaps. If you rely on the ESR channel, the matching 153.5 and 115.43.0 builds cover you with the same protections. Users with high-contrast setups or a taste for modern image formats get the biggest day-to-day payoff.
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- Mozilla Firefox on UpdateStar
- Alternatives to Mozilla Firefox, including Google Chrome, Brave Browser and Opera Browser
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