Firefox 156 is out with faster start-up times for its built-in PDF viewer and lower CPU usage when viewing large JPEG images.

As you browse the web you (pretty much always) see images smaller than their native resolution. To wit, if I embed a 4K JPEG in this post, for example, you don’t see it at full size: it’s downscaled to fit on the page. Same amount of pixel data, but squeezed by CSS.

In Firefox 156, the browser now uses libjpeg-turbo’s IDCT scaling to reduce images during decoding, rather than loading a full-size image into memory and then shrinking it.

Benchmarks from the bug report show up to 20× less memory used during very large image loading, and decoding is up to twice as fast. Since these speeds were quite fast already, there’s no perceptible difference to users. Behind the scenes, it’s more efficient.

Firefox’s built-in PDF viewer starts up to 45% faster in this release. The browser now loads the background PDF.js worker sooner, rather than launching it only when needed.

Sponsored suggestions in the address bar are live for users in France, Germany and Italy (Ouais!, Juhu!, etc). These are already available in some other locales. Don’t want them? Disable them via Settings > Search > Firefox Suggest > Suggestions from Sponsors.

Besides that, the rest of this release is primarily bug fixes – worthwhile and welcome as always.

• Dragging images in rich-text editors often replaced it with text
• FLAC audio in MP4 failed to play on sites like Bilibili
• Subtitles didn’t load in Picture-in-Picture if enabled after PIP opened
• Bookmarks moved outside their folder if dragged as a group (sidebar)
• HTTP sites failed to load when DNS over HTTPS was enabled

One that stung me in v155 has been patched: the browser losing all network connectivity if the built-in free VPN was enabled.

Plus, a fresh set of security patches.

This is the second release since Mozilla moved to a twice-monthly release schedule. Firefox 157 will be released in 2 weeks time and, if all goes to schedule, make Firefox’s new Nova redesign default.

Firefox 156 is available to download from today (Monday, 14 September) from the Mozilla FTP (if you fancy going direct), and rolls out as an update on 15 September.

Existing user? On Windows and macOS, or the Linux Firefox binary, you can update in-app. Otherwise, wait the update to roll out through a repo, software manager or app store. 

Ubuntu users get this – all all other – update as an automatic background update from the Snap Store. Nothing to go hunting for as a notification prompts you to restart to install the update as soon as it’s ready.