Mozilla has officially released Firefox 145 on November 11, 2025, bringing significant changes and new features to the popular open-source web browser. This update marks an important milestone for Linux users with both exciting additions and notable changes in platform support.
Major Change: End of 32-Bit Linux Support
The most significant change in Firefox 145 is the discontinuation of support for 32-bit Linux systems. Mozilla has stopped building and offering 32-bit builds of Firefox starting with version 145.
According to Mozilla, “32-bit Linux on x86 is no longer widely supported by the vast majority of Linux distributions, and maintaining Firefox on this platform has become increasingly difficult and unreliable.”
The company recommends users to install a 64-bit version of Firefox for continued updates and security patches. This decision allows Mozilla to focus resources on delivering the best and most modern Firefox experience.
PDF Annotation Feature
Firefox 145 introduces a powerful new PDF annotation capability. Users can now add, edit, and delete comments directly on PDF files opened in the browser. This feature is perfect for:
- Recording summaries and notes
- Marking important questions
- Creating task lists within documents
The comment sidebar makes it easy to scan all annotations and jump to specific comments quickly, which is especially useful for long or heavily marked-up documents.
Tab Group Preview Enhancement
Managing multiple tabs becomes easier with the new tab group preview feature. Users can hover over a tab group name to instantly see which pages are inside without needing to expand the group. This simple addition improves workflow efficiency for users who organize their browsing sessions with tab groups.
Enhanced Link Sharing
Firefox 145 updates the “Copy Link to Highlight” context menu feature, allowing users to share specific sections of a webpage with others. Users can select any portion of a webpage, right-click, and copy a link that will take recipients directly to that highlighted section.
Semantic History Search (Experimental)
One of the most innovative features in Firefox 145 is Semantic History Search, currently available in Nightly and Early-beta builds. This experimental feature enables users to find previously visited pages using natural-language or concept-based queries.
For example, instead of remembering exact URLs or page titles, users can search for “that Linux article about Varnish” and Firefox will understand the context. The feature works by:
- Downloading a small language model (Xenova/all-MiniLM)
- Creating a vector database based on browsing history
- Processing all searches locally on the device
All matching happens on-device with no data collection or external data transmission, ensuring complete privacy protection.
User Interface Improvements
Firefox 145 brings several visual refinements:
- Horizontal tabs now feature slightly rounded corners matching the vertical tabs style
- Buttons and text inputs across all settings have been refined for consistency
- The address bar has been updated for better visual cohesion
When no extensions are installed, clicking the Extensions button now displays helpful suggestions and links to the Firefox Add-ons store.
New Tab Management Option
A new setting has been added in General > Tabs that allows users to “Open links from apps next to your active tab.” This gives users more control over how external links open in Firefox.
Developer Improvements
Web developers will appreciate several technical enhancements as detailed in the official developer release notes:
- Support for Atomics.waitAsync proposal for thread synchronization based on shared memory location values
- Support for the new Integrity-Policy HTTP header for enforcing script subresource integrity
- Matroska (.mkv) compatibility for codecs including AVC, HEVC, VP8, VP9, AV1, AAC, Opus, and Vorbis
- Support for the text-autospace CSS property for better character spacing across mixed writing systems
Enhanced Privacy Protection
Firefox 145 introduces second-phase anti-fingerprinting defenses, reducing the risk of users being identified and tracked online. These protections are initially enabled in Private Browsing Mode and Enhanced Tracking Protection (ETP) Strict Mode.
Mozilla is carefully balancing enhanced privacy protection with website usability. Users can manually disable protection on specific sites if they encounter compatibility issues.
How to Download Firefox 145
Firefox 145 is now available for download from Mozilla official FTP server. The release includes:
- 64-bit builds for Linux systems
- ARM64 (AArch64) builds for compatible devices
- Builds for Windows and macOS
Windows and macOS users can expect an over-the-air update within the following days. Linux users on rolling-release distributions can expect Firefox 145 to appear in their repositories soon.
Recommended Action for 32-Bit Linux Users
If you are currently using 32-bit Linux, Mozilla strongly encourages upgrading to a 64-bit operating system and the corresponding Firefox version. The 32-bit version will no longer receive updates or security patches.
For users who cannot immediately upgrade, Firefox ESR 140 will continue to receive security updates through at least September 2026.
Conclusion
Firefox 145 represents a forward-looking release that drops legacy platform support while introducing innovative features like Semantic History Search and PDF annotations. The enhanced privacy protections and user interface refinements demonstrate Mozilla’s commitment to delivering a modern, secure browsing experience for Linux users.
Whether you are a casual user or a web developer, Firefox 145 offers meaningful improvements that enhance both productivity and privacy.
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