Firefox 101 Stable: security fixes and classic download behavior restored

Mozilla plans to release Firefox 101 to the Stable channel on May 31, 2022. The new version of the open source web browser is a smaller release that includes some improvements and security fixes.

firefox 101

Mozilla released updates to Firefox's other channels as well. Firefox 91.10.0 ESR, Extended Support Release, and Firefox 101 for Android have been released as well. All development channels of the browser have been upgraded next to that: Firefox Beta and Developer were moved to version 102, and Firefox Nightly to version 103.

Executive Summary

Firefox 101 Stable is a security update that addresses security issues in the browser.
Firefox 102 is the next ESR release. It will be released next month.

Firefox 101.0 download and update

firefox 101 release

Firefox 101 is available already. The browser's built-in updating system may not pick up the update at the time of writing, but it should become available later on May 31, 2022. If you are reading this after May 31, you should receive the update immediately when you run a check for it.

Select Firefox Menu > Help > About Firefox to display the installed version of the browser. Firefox runs a check for updates when the window opens to download and install any update that it finds.

Here are the links to the official download repositories.

Firefox 101.0 new features and improvements

Return of the classic download prompt

firefox open or save files

The big new improvement in Firefox 101 is one that is not highlighted in the official release notes. Mozilla changed the download behavior of the browser in Firefox version 97, which it released in January 2022.

Firefox used to display a prompt to the user, giving them options to open or save the file. The new download prompt copied the behavior of Chromium-based browsers; this meant that Firefox started the download immediately.

While there was an option to modify the behavior by enabling "always ask you where to save files" in the preferences, it did not replicate the full functionality of the classic download prompt.

Now, with Firefox 101, comes an option to restore the old prompt:

Load about:preferences in the Firefox address bar.
Scroll down to the Applications group on the page.
Switch the default option "save files" to "ask whether to open or save files" on the page.

Other changes

Mozilla notes that Firefox users may assign custom actions to any "non-configured MIME type" after download completion.
Firefox supports using multiple microphones during video conferencing. The browser supports switching between microphones, provided that the conferencing service provider supports the functionality.
Firefox for Android supports using a magnifier for forms on Android 9 and later, which improves the usability of forms in the browser.

Developer Changes

Sites may use the prefer-contrast media query to determine if a user has requested a higher or lower contrast.
The viewport sizes small, large and dynamic have been introduced
Constructable stylesheets are now supported.
AV1 codec parameters are parsed properly now in media support queries.
The WebDriver BiDi protocol is enabled by default in this version of Firefox
Several Manifest V3 APIs and changes added:
- Scripting API added for add-on developers, "which provides features to execute a script, insert and remove CSS, and manage the registration of content scripts".
- Action API added, "which takes over the features of the browserAction API in Manifest V3 extensions".
- Addition of the "host_permissions" manifest key, which is available for Manifest V3 extensions.
- The "background" manifest key property "persistent" can be set to false under the control of preferences: for Manifest V2, the extensions.eventPages.enabled preference, and in Manifest V3, the extensions.manifestV3.enabled preference.
- Content script execution environment has changed for Manifest V3 extensions.

Enterprise changes

Known Issues

none listed.

Security updates / fixes

Security updates are revealed after the official release of the web browser. You find the information published here after release.

Outlook

Firefox 102 will be released on June 28, 2022, according to the release schedule; this marks the launch of the new Firefox ESR base version as well. Firefox ESR 91.x will reach end of support on September 20, 2022.

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