La Firefox version 139 is now available for early download, bringing with him, four weeks after the v138, a variety of tweaks and new features for both the general user and developers. Although its official release is set for May 27, 2025, binaries are already available from the official Mozilla servers.
In this edition, Mozilla is committed to fine-tuning the browsing experience and explore new approaches in search, machine translation, and personalization. It's an update with notable, though not massive, changes that seeks to improve everyday life and open the door to innovations driven by artificial intelligence.
Perplexity AI: An Experimental Twist on Firefox Search 139
One of the most striking movements of Firefox 139 is the testing phase in which integrates Perplexity, an artificial intelligence-powered search engine, appears directly in the address bar when the user clicks on Search mode. A message appears inviting them to try "a new way to search in Firefox" using Perplexity, whose answers are conversational, direct, and accompanied by source citations.
This novelty means that Instead of simply providing links, Perplexity synthesizes information and answers questions interactively., helping to reduce search engine overload and facilitating access to accurate data. It hasn't been specified exactly which segment or regions of Firefox 139 users will be affected by this experiment, nor how long it will last, but it's interpreted as a step by Mozilla to explore alternatives beyond the traditional agreement with Google, on which its default search engine currently relies.
At this time, there is no public confirmation of any financial agreements between Mozilla and Perplexity, although the collaboration could change depending on the results and user interest. Furthermore, the browser is expected to soon require users to accept new terms of use upon launch.
Performance improvements and new features
El Performance when uploading files via HTTP/3 has improved significantly Compared to previous versions, users using high-speed or high-latency connections, especially those using QUIC 0-RTT reconnects, should notice faster file loading times.
As for translation, you can now do full translations within extension pages (those that start with moz-extension://), a recurring community request. This makes it easier to navigate in different languages, even within the browser's own tools. Additionally, PNG images pasted into Firefox maintain transparency, making it easier to work with images in different workflows.
As an optional feature in gradual rollout, the advanced customization of new tabs: You can use your own images as a background or choose custom colors, including new thematic categories. Along with this, link previews (experimental feature enabled through Firefox Labs) and improved support for expanding closed sections (such as details) in on-page searches.
Contributions for developers and privacy
For those working on web development, version 139 adds support for Timers in Workers, the WebAuthn largeBlob extension, the “hidden=until-found” attribute —which helps to search for hidden content—, and the method requestClose() all with <dialog>These improvements expand the capabilities of modern web applications, while also keeping up with the latest trends in cross-browser interoperability.
The native editor for elements with has also been updated. contenteditable y designMode to handle white space more consistently with other browsers like Chrome, and privacy features—such as the addition of Service Workers to private browsing mode—are strengthened, allowing for more advanced and secure use.
Finally, the usual bug fixes and security patches are included., essential for maintaining data protection and stability. Although Chrome passwords and payment methods can no longer be automatically imported starting with this version, it is still possible to import passwords using CSV files.
Version 139 also coincides with the release of the ESR releases (128.11 and 115.24), designed for environments where stability is key. The rollout will be gradual, and it's recommended to review the release notes for each update to take full advantage of the new features.
Firefox 139 introduces new tools, speed, and AI-powered experiences, while maintaining its focus on security and customization. Those who want to get ahead of the official announcement can download the browser now from Mozilla's website and explore all the new features.