Firefox 156 Opens PDFs 45% Faster and Adds ARM64 Hardware Video Decoding

by Geth Author

Mozilla released Firefox 156 on September 15, 2026 to the stable channel. The most visible change is a PDF viewer that now initializes up to 45% faster — a meaningful improvement for anyone who regularly opens PDF documents in the browser.

The speedup comes from changes to how PDF.js, Firefox's built-in PDF renderer, initializes its rendering pipeline. The 45% figure is from Mozilla's internal benchmarks and will vary by document complexity and hardware, but the improvement is consistent across machines. PDF loading has been a persistent area where Firefox trails Chromium-based browsers, and this update closes a noticeable part of that gap.

ARM64 Windows Gets Hardware Video Decoding

On Windows ARM64, Firefox 156 switches WebRTC video calls from software-decoded H264 to hardware H264 decoding. This matters most for users on Qualcomm Snapdragon laptops and the growing range of ARM-based Windows PCs: hardware decoding is significantly more power-efficient than software decoding, which translates directly to longer battery life during video calls. If you use Firefox for video conferencing on one of these machines, the difference in thermal behavior and fan noise should be noticeable.

Memory and Image Handling

Mozilla improved memory and CPU usage when rendering large JPEG images scaled down to fit the viewport — a common pattern on photo-heavy news sites, image galleries, and social feeds. The fix reduces unnecessary memory allocation for pixels that will never be displayed, which helps on lower-memory devices and keeps the browser responsive when multiple image-heavy tabs are open.

macOS Autostart and Regional Search Expansion

Firefox 156 adds macOS autostart support. Users can now configure Firefox to launch at login from the Startup section of Firefox Settings. The option is off by default, but it matches a feature that Chrome and Safari have offered on macOS for years — removing one reason to switch browsers for users who want their browser ready when the machine wakes up.

The address bar's search and recommendation features are now available in France, Germany, and Italy, expanding beyond the English-language markets where the system launched. The feature surfaces contextual suggestions based on browsing history and open tabs.

Security

As with every Firefox release, the security notes matter. MFSA 2026-90 documents patches for privilege escalation issues, use-after-free flaws, incorrect boundary conditions, site isolation bypasses, and sandbox escapes. Organizations running older Firefox ESR versions should review the advisory to assess their exposure.

Firefox 156 is available now via the browser's built-in updater or at mozilla.org/firefox.