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⇱ Firefox 139.0 Now Available With Faster HTTP/3 Upload Performance - Phoronix


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Firefox 139.0 Now Available With Faster HTTP/3 Upload Performance

Written by Michael Larabel in Mozilla on 26 May 2025 at 06:34 AM EDT. 15 Comments
Mozilla Firefox 139.0 release binaries have been pushed out to mirrors today ahead of the formal announcement tomorrow. With the Firefox 139 browser update comes a few new features worth mentioning.

Firefox 139 delivers faster upload performance on HTTP/3 connections to the point that it's "significantly improved." Especially for HTTP/3 connections involving QUIC 0-RTT resumed connections and high bandwidth and high delay connections, HTTP/3 uploads should be much faster on Firefox 139 than with prior Mozilla Firefox releases.

Firefox 139 also includes full-page translation support within Firefox extension pages, PNG images with transparency are now preserved when pasting into Firefox, support for the WebAuthn largeBlob extension, timer throttling for workers, and support for the "hidden=until-found" attribute for content to be found in the via find-in-page but not otherwise displayed by default.

👁 Firefox 139 on Linux


Some of the new experimental web features of Firefox 139 that are available but disabled by default include prioritized task scheduling, View Transition API, and disabling non-standard beforescriptexecute / afterscriptexecute events.

Those wanting to grab the official Mozilla Firefox 139.0 release binaries right now can do so via ftp.mozilla.org.

Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via MichaelLarabel.com.