Version 98.0a1, first offered to Nightly channel users on January 10, 2022
Firefox Nightly gets updated every day and as a consequence, the release notes for the Nightly channel are updated continuously to reflect features that have reached sufficient maturity to benefit from community feedback and bug reports.
Warning: Features listed here may or may not make a final release of Firefox.
In addition to these release notes, you can follow ongoing development on our @FirefoxNightly Twitter account as well as read our Nightly Blog.
Firefox now has a new optimized download flow. Instead of prompting every time, files will now download automatically. They can still be opened from the downloads panel with just one click. More information
New Nightly-only setting: Show fewer update notification prompts. When the setting is enabled and Nightly is ready to restart to install updates, it will show a notification in the hamburger menu but not a popup notification. Additionally, if the user also has the Check for updates but let you choose to install them" setting enabled, the Update Available* notification will be shown in the hamburger menu but the popup notification will be suppressed for up to a week after the last successful update.
The use of webRequest used to cause addons to start early during Firefox startup. This has changed to only use webRequest blocking calls. non-blocking calls no longer cause an early startup for addons.
The Compatibility sidebar panel in the DevTools Inspector already available on pre-release channels will become available on the release channel in version 98 . It provides compatibility warnings for the CSS properties used on the selected element, as well as for the overall page.
Developers may use it to detect web-compatibility issues early, without having to test in each browser. All compatibility data are pulled from MDN.
With Firefox version 100 rapidly approaching, you can help test websites' compatibility with three-digit version numbers by enabling the new Firefox 100 User-Agent String option in the Experimental section of Settings (about:preferences#experimental). If you find a website that is broken with Firefox version 100, please file a bug report on webcompat.com.