ZMI ALPHA:Here is what is new and changed in Firefox 84.0

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ZMI ALPHA:Here is what is new and changed in Firefox 84.0

Firefox 84.0 Stable and Firefox ESR 78.6 will be released later today (if you are reading this on December 15, 2020). The new versions of the Firefox web browser will be distributed via the browser’s automatic updating system and also as direct downloads from the Mozilla website.

All development versions of Firefox are updated as well to new versions. Firefox Beta and Firefox Developer are updated to version 85, Firefox Nightly to version 86. Firefox for Android follows the stable version’s release scheme and will be upgraded to version 84.0 as well.

Firefox 84.0 is the last major release of 2020.

Check out the Firefox 83.0 release notes if you missed them.

Executive Summary

  • Firefox 84.0 includes security fixes
  • This version is the last to support Adobe Flash.
  • Optional add-on permissions can now be controlled via about:addons.

Firefox 84.0 download and update

Firefox 84.0 and Firefox 78.6 ESR upgrades are available via the automatic updating system and as standalone downloads. Firefox users may run manual checks for updates by selecting Menu > Help > About Firefox.

Firefox displays the installed version and runs a check for updates when the page is opened.

Manual downloads are also available. The following pages list direct downloads for supported Firefox channels (will be available later on December 15, 2020)

New features and improvements

Manage Optional Permissions in the Add-ons Manager

firefox revoke optional permissions

I reviewed this feature when it landed in Firefox Nightly in October, and you may want to check out the review for details.

Firefox extension developers may request optional permissions for extra functionality, e.g. when the user enables a new feature in the options. The problem up until now was that these optional permissions were not listed on the add-ons management page about:addons and users had no option to revoke optional permissions unless the extension author added such functionality to the extension.

Starting in Firefox 84, users may now manage optional permissions on about:addons. These permissions can be revoked directly from there. Note that revoking permissions may break certain functionality of the extension.

Native Apple Silicon CPU support

Mac users who run Firefox on devices with Apple Silicon CPUs may notice “dramatic performance improvements” compared to the non-native Firefox 83.0 build according to Mozilla.

The organization notes that Firefox’s launch time has improved significantly (over 2.5 times faster compared to Firefox 83) and that web apps are “twice as responsive”.

Mac users who upgrade to Firefox 84 need to fully close Firefox after installing the Firefox 84.0 upgrade to ensure that Firefox 84.0 runs on the new architecture; that this is the case can be verified by opening about:support and searching for “Rosetta Translated”. If the value is false, the new architecture is used.

Other changes

  • localhost URLs will no longer be treated as mixed content so that loaded resources are “now assumed to have been delivered securely”.
  • It is now possible to zoom extension panels, popups, and sidebars by holding down Ctrl and using the mouse wheel.
  • WebRender rolls out to Mac OS Big Sur and Windows devices with Intel generation 5 and 6 GPUs.
  • An accelerated rendering pipeline is available for Linux/GNOME/X11 users.
  • Firefox 84.0 is the final release to support Adobe Flash.
  • Preferences policy was updated to support preferences beginning with “spellchecker and pdfjs”.
  • Windows uninstaller no longer asks for UAC permissions.

Firefox for Android

  • WebRender rollout continues, this time to devices with Mali-G GPUs.
  • Downloaded files can now be deleted from within Firefox.
  • View open tabs side by side using grid view.
  • Scrolling accuracy and control improvements.

Developer Changes

  • Firefox Accessibility Inspector supports displaying the keyboard tab order on a web page
  • Paint Timing API PerformancePaintTiming interface added.
  • Application Cache has been removed. Mozilla suggests that developers use the Service Worker API instead.
  • Network panel handles unexpected crashes in the new release to provide useful debugging details.

Known Issues

Two Mac OS issues are listed:

  • Users may encounter playback errors on encrypted content if the Rosetta system software is not installed.
  • Firefox installations may get corrupted if the Cylance antivirus software is installed as it flags Firefox as malware erroneously.

Security updates / fixes

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


The Firefox 85.0  release date is January 26, 2021; this is the first version of Firefox without Adobe Flash support, or in fact, any NPAPI support.

Recently Reviewed Firefox extensions

New Section; we highlight reviews of Firefox add-ons since the last stable release of the browser here.

Additional information / sources


Here is what is new and changed in Firefox 84.0

Article Name

Here is what is new and changed in Firefox 84.0


Information about the Firefox 84.0 and Firefox 78.6 ESR releases that Mozilla released on December 15, 2020 to the public.


Martin Brinkmann


Ghacks Technology News



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