Firefox is a popular web browser
Mozilla announced the official release of the new version of "Firefox 154", an update that incorporates a wide range of adjustments aimed at protecting connections on local networks, optimizing tab management through artificial intelligence, and offering new capabilities to web developers.
Alongside this release, the organization has published maintenance updates for its Extended Support Branches (ESR), delivering versions 153.1.0, 140.14.0, and 115.39.0. Additionally, the Mozilla development team has patched 167 vulnerabilities in this release.
Main new features of Firefox 154
The new version of Firefox features security improvements, with the Local Network Access (LNA) specification for WebSocket connections being the most significant. Historically, public web applications could attempt to establish connections with devices within a user's internal network. Now, Firefox restricts access to loopback addresses and private network ranges by default.
In other words, if a website tries to open a WebSocket to a local resource, the browser will stop the action and display a dialog box requesting explicit permission.
Tab management, privacy, and multimedia
Firefox 154 introduces "Smart Window" mode, a progressive rollout feature that uses artificial intelligence to analyze open tabs, group them logically according to their context , and suggest names for each group.
To facilitate control of these new features, the address bar includes a quick access button called "Manage AI," which leads directly to the corresponding settings panel. Meanwhile, the native full-page translation tool can now translate content embedded within HTML frames (<iframe>), performing language identification during the initial site load for a faster response.
Regarding multimedia performance, the browser engine has been optimized to significantly accelerate searching and scrolling in the timeline when playing videos. Additionally, Windows users now have official support for running the NVIDIA GeForce NOW cloud gaming platform directly from the browser.
New Web Standards
For content creators and web developers, this version implements recent features of the CSS, HTML, and JavaScript standards. The rendering engine adds support for the CSS properties `text-box-trim` and `text-box-edge`, which provide mathematical control over the top and bottom margins of fonts, allowing for precise vertical alignment without relying on spacing tricks.
Also included are the CSS functions `sibling-index()` and `sibling-count()`, which allow for conditional styling based on an element's position relative to its sibling elements in the DOM tree. Regarding HTML form structure, Firefox now displays a native graphical interface for selecting the time when using the `<input type="time">` and `<input type="datetime-local">` tags.
At the network and data processing level, the browser already interprets the HTTP No-Vary-Search header. This directive allows servers to indicate which URL parameters are irrelevant to the content, enabling the browser to reuse page versions stored in the disk cache and improving load times.
On the JavaScript side, the Iterator interface is updated with new synchronous execution methods, such as `.chunks()` for splitting elements into groups, `.windows()` for sliding window iterations, `.includes()` for direct content validation, and `.join()` for concatenating results into strings. Finally, the integrated JSON file viewer simplifies debugging by displaying the full path (breadcrumb) of the selected element at the bottom of the screen.
Interface fixes and known bug fixes
The development cycle also focused on refining the graphical interface across different operating systems. A bug in macOS where closing the browser left an invisible window that captured mouse clicks was fixed, and multiple issues in the Windows taskbar related to automatic hiding and picture-in-picture window display were corrected. The behavior of the "Firefox View" button was also modified; it has been removed from the default toolbar for new or inactive profiles, although it can be restored from the customization menu.
Finally, it's worth mentioning that two issues are currently being addressed : some users may experience temporary address autofill failures due to recent adjustments to the autofill logic, and instances of slow performance or unexpected master password prompts when accessing the browser's credential store. Mozilla indicates that mitigations for both issues have already been deployed and they continue to monitor the stability of the browser.
How to install or update to Firefox 154
If you already have Firefox installed, the update should arrive automatically through your distribution's package manager in the next few days. However, if you want to get version 154 immediately without waiting for the official repositories , the best option is to use the official binary provided by Mozilla.
To install it from the binary on any Linux distribution (Ubuntu, Fedora, Arch, etc.), you can follow these steps in your terminal:
wget -O firefox.tar.bz2 "https://download.mozilla.org/?product=firefox-latest&os=linux64&lang=es-ES" sudo tar xjf firefox.tar.bz2 -C /opt/ sudo ln -sf /opt/firefox/firefox /usr/bin/firefox
If you prefer to use Snap packages (common in Ubuntu), you can force the update with:
Sudo Snap Refresh Firefox
For users who prefer Flatpak and Flathub, the update can be performed by running:
flatpak update org.mozilla.firefox
For users of Ubuntu, Linux Mint, and other Ubuntu derivatives, it's also possible to update Firefox via the official PPA . To do so, open a terminal and enter the following commands:
sudo add-apt-repository ppa:ubuntu-mozilla-security/ppa -y sudo apt-get update sudo apt install firefox
Finally, if you prefer to wait for it to arrive in your distribution's native repositories (DNF, Pacman), you just need to run your system's usual update command, although keep in mind that this can take anywhere from a few hours (on Arch) to several days (on Debian/Ubuntu).