Almost a month after releasing version 138, Mozilla has launched Firefox 139, the latest update to its popular open-source web browser, now available for download.
The main highlight of the new version is that Firefox can now perform full-page translations inside extension pages, not just on ordinary websites.
Moreover, PNG images keep their transparency when pasted into the browser, a quality-of-life tweak designers have requested for ages.
Uploading large files should also feel snappier on high-bandwidth, high-latency lines, thanks to better HTTP/3 performance during 0-RTT resumption.
Under the hood, there are some interesting additions targeting developers, and more specifically:
- Temporal API enabled by default – Firefox becomes the first major browser to ship the long-awaited replacement for JavaScript’s quirky
Dateobject, promising far saner date-time handling for web apps. - Service Workers in Private Browsing – Encrypted storage now lets background tasks run even while users stay in private mode, expanding what PWAs can do without compromising privacy.
- WebAuthn largeBlob extension – Sites that store credential-bound blobs (think encrypted keys or extra metadata) get first-class support.
requestClose()for<dialog>, timer throttling for Workers, andhidden=until-foundall become available, each nudging Firefox closer to spec parity with Chromium.- Enhanced searchability of closed
<details>elements and correct text serialization fromwindow.getSelection().toString().
Those eager to immediately download the latest version of Firefox can do so directly from Mozilla’s server.
Windows and macOS users can expect an over-the-air update within the next day. Users of rolling-release Linux distributions should look for Firefox 138 as an update in their repositories over the next few days.
