What’s New in Firefox 157.0?
Mozilla has released Firefox 157.0, and this version comes with one of the most important interface changes in recent years. The update, available since September 29, 2026, brings a browser with a modernized visual appearance, a new compact display mode, new themes, and several improvements for video calls, security, and compatibility with web standards.
The most obvious change is the new Nova design, which alters the appearance of the toolbars, tabs, menus, and sidebar. Beyond the aesthetic aspect, Firefox 157 also includes some interesting technical changes, especially for WebRTC video calls and HDR content playback.
This article outlines the main new features in Firefox 157.0, explained in a way that is understandable to all users, as well as some useful details for those interested in the technical side.
The new Nova design changes the look of Firefox
The most visible novelty in Firefox 157 is the new interface, called Nova.
Mozilla has revamped several components of the browser to have a more unified appearance. The changes are reflected in the toolbars, tabs, menus, sidebar, and various control elements.
In other words, it’s not just about changing the color scheme or appearance. Mozilla has rethought how the various elements of the interface combine and behave visually.
For the user, the result is a Firefox browser that looks different from previous versions, but still retains the main functions that it used before.
Another advantage of the new design is that users can more easily customize the browser’s appearance.
Compact Mode offers more space for websites
A practical novelty brought by Firefox 157 is Compact Mode. After activating this mode, the spaces between interface elements, including between the toolbar and tabs, are significantly reduced. Thus, a larger portion of the screen remains available for the webpage you are visiting.
This feature can be particularly useful on laptops or smaller monitors. It is equally interesting for people who work with two windows side by side and want to minimize the space taken up by the browser interface.
For a large monitor, the difference may seem minor. However, on a laptop with a smaller screen, a few pixels gained vertically can become surprisingly useful.
Firefox 157 introduces new themes
Mozilla has also added new built-in themes, available in light and dark variants.
The advantage is simplicity: the user can quickly change the browser’s appearance without searching for and installing a separate theme.
These themes are part of the new visual direction Nova and complement the changes made to the Firefox interface.
WebRTC video calls receive AV1 hardware decoding support
One of the most interesting technical changes in Firefox 157 concerns video calls made via WebRTC.
On compatible devices, Firefox can now use hardware decoding for AV1 videos received during video calls, instead of always processing this data using the CPU.
What does this mean in practice?
When participating in a video call, the browser needs to transform the compressed video stream received from the other party into an image that can be displayed on the screen. If this operation is handled by the device’s specialized hardware, the CPU can be less taxed.
Mozilla is thus aiming for more efficient resource usage, especially on devices that have hardware support for AV1.
However, it is important not to interpret this change as an automatic improvement for all video calls. For it to take effect, the service used must employ AV1, the device must support AV1 hardware decoding, and Firefox must be able to effectively use that decoder.
Firefox 157 becomes more transparent regarding monitored HTTPS traffic
Version 157 also brings a change focused on security and privacy.
If Firefox is configured to log the encryption keys used for web traffic, the browser now displays a warning. This can be seen in the site information panel, accessible from the protection icon in the address bar, as well as in Settings.
Why is this important?
In certain situations, software installed on the same computer may intercept and analyze HTTPS traffic. This can be legitimate in a management or troubleshooting environment, but the user should be aware that such a configuration exists.
With the new warning, Firefox makes this situation more visible.
Firefox Suggest expands to more European countries
The Firefox Suggest feature, which provides suggestions when you enter a search or address in the browser’s bar, has been expanded to several European countries.
These include Austria, Belgium, the Czech Republic, Denmark, Finland, Hungary, Ireland, Luxembourg, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, and Switzerland.
Suggestions can be controlled from the Firefox Suggest settings, allowing users to decide what types of suggestions they wish to receive.
The Firefox sidebar has been updated
The sidebar also receives an important change in Firefox 157.
The new version of the sidebar is now enabled for all users. Those who were using the older version will still find a familiar structure, but the panel switcher is moved to the top.
Mozilla has also removed the “Show sidebar” option from Settings.
Advanced users who prefer the old version can still temporarily revert to it by about:config, setting sidebar.revamp to false. Mozilla states that this option will remain available until the end of 2027. Disabling the new system also targets vertical columns.
For the average user, however, the recommendation is to first test the new interface before changing advanced settings.
More video playback issues have been resolved
Firefox 157 also includes a series of fixes for multimedia. One of the resolved issues affected certain HDR videos in 8-bit color format on Windows. In some cases, instead of being displayed correctly, they could appear washed out or gray.
Mozilla has also improved synchronization between image and sound when the playback speed of a video is changed repeatedly. The issue could be observed, for example, when the user frequently changed the speed of a video.
Problems that could cause the image transmitted by certain phones or tablets during WebRTC calls to appear rotated or even upside down have also been resolved.
Also in the video section, Mozilla has fixed an issue on Windows where the taskbar could remain visible over a video played in full screen.
Keyboard navigation
Firefox 157 also brings a seemingly small but useful change for those who navigate using the keyboard.
When you press Tab in the address bar or search bar, the cursor now goes directly to the field where you can enter text. Previously, the focus could stop first on the search engine button.
The button can still be accessed using Shift + Tab.
It’s the kind of change that most users probably won’t notice, but it can make navigation faster for those used to predominantly working with the keyboard.
Amazon is no longer included in the default search engines list
Mozilla has removed Amazon from the list of search engines included by default in Firefox. It’s important to note that this change does not mean that Amazon can no longer be used for searches.
Users can still manually add it as a custom search engine from the browser settings.
Websites can better control the appearance of certain windows
Firefox 157 makes certain native elements of the browser, such as windows generated by alert(), confirm() and prompt(), color and date selectors, or autocomplete lists of forms, better take into account the light or dark theme of the webpage.
For the user, the result is a more coherent experience when navigating websites that use dark or light themes.
It’s a change that is rather subtle, but it contributes to a better integration of the browser interface with the design of modern websites.
What’s new for web developers in Firefox 157?
Firefox 157 is not only important for regular users. The new version also brings some relevant changes for web developers.
One of these is support for the CSS function at-rule() within @supports. This allows for checking the browser’s compatibility with certain CSS rules.
Firefox 157 also adds support for the value chain of the CSS property overscroll-behavior.
These changes are less visible to the average user, but they are important for developers who are tracking compatibility with the latest features of the web platform.
Firefox 157 also includes security fixes
In addition to new features, Mozilla has also included more security fixes in Firefox 157.
This is a sufficient reason for users not to postpone the update just because they are not interested in the new design.
A browser is one of the applications that interacts most frequently with content from the internet. Keeping it up to date is, therefore, important for both compatibility and security.
Is it worth updating to Firefox 157?
Yes, Firefox 157.0 is an important update, especially for users who want a modernized interface and for those who frequently use video calls or have limited screen space configurations.
Source: firefox.com
