SNACK: 3-line summary
- Firefox 158 has reached the desktop Release channel with JPEG XL image support.
- PDF output gains accessibility improvements and fixes for missing math symbols, and the update includes security patches.
- Smart Window form suggestions are rolling out gradually, so updating does not guarantee immediate access.
Firefox 158 reached the desktop Release channel on October 13, 2026. The update lets the browser display JPEG XL images natively and makes saved PDFs more accessible—useful changes for viewing images and keeping readable copies of web pages.
Snackgirls react
AIKO: I’m curious how sites will use JPEG XL now that Firefox supports it natively. Image-format compatibility is an interesting puzzle of its own.
Nea: I’d like to save game-lore reference pages as readable PDFs, formulas included. Those are the little details I’d want to revisit.
JPEG XL images and more accessible PDFs
Firefox now supports the JPEG XL image format. Mozilla says it generally offers better compression than WebP, JPEG, PNG and GIF; that does not mean every image on the web will load faster.
Firefox also creates more accessible PDFs when you save a page as a PDF and when you print on Linux or macOS. PDF rendering fixes include previously missing mathematical symbols.
Smart Window can suggest information for forms
In Smart Window, clicking a form field or selecting “Fill from sources” can bring up suggested information drawn from relevant open tabs and saved autofill data.
These form suggestions are being rolled out gradually. Firefox 158 is already available, but installing it does not guarantee that the feature will appear immediately.
Security fixes and a PWAsForFirefox startup workaround
Mozilla’s security advisory lists 77 CVE entries fixed in Firefox 158, including 30 rated high impact. Mozilla has changed how it reports internally identified memory-safety bugs, assigning individual CVEs instead of grouping them under one. The total alone therefore does not establish an increase in risk over earlier versions.
Web apps launched through the third-party PWAsForFirefox tool may fail to start in Firefox 158 with the message “The installation seems to be incomplete.” Update PWAsForFirefox to version 2.20.1 or later. If the error persists, open the PWAsForFirefox extension settings and select “Reinstall runtime” followed by “Patch profiles and runtime”.
Sources and checked date: October 18, 2026
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