Firefox ESR 91: new ESR version will be released tomorrow

Mozilla plans to release new versions of its Firefox web browser on Tuesday 10, 2021. The organization does so every 4-weeks on average, but tomorrow's release is special, as it is the base for a new ESR, Extended Support Release, version of the web browser.

Firefox ESR versions are maintained for a longer period compared to stable releases. One core difference is that they are released with a specific feature set that is not changed during the lifetime. Security updates and bug fixes are released, but features are not added usually until the next ESR version is released.

The last Firefox ESR version, Firefox 78 ESR, was released in June 2020, and it replaced Firefox 68 ESR in September 2020.

Two Firefox ESR branches are released side-by-side for a period of two or three releases usually, before the older one is not updated anymore; this gives organizations and home users enough testing and migration time.

Firefox 91 ESR won't replace Firefox 78 ESR right away. The latter will see two additional releases, Firefox 78.14 ESR and Firefox 78.15 ESR before it will be discontinued; this will happen in October 2021.

Firefox 91 ESR marks the beginning of a new base for extended support releases. The version will be supported for about a year.

Organizations and home users who are running the current ESR version may update their installations to the new version. The upgrade is a major one, considering that Firefox 91 includes all the functionality that Mozilla introduced since the release of Firefox 78 ESR.

Major changes include the new interface design that Mozilla rolled out recently, improved privacy protections, removed Adobe Flash support, support for new operating system versions, e.g. Mac OS Big Sur, and a lot more.

Here is a short list of changes that will be introduced in Firefox 91 ESR:

• Firefox 90 does not support the FTP protocol anymore.
• Mozilla introduced a new interface in Firefox 89.
• Windows background updates are supported.
• Firefox 87 introduces support for SmartBlock feature.
• Firefox 86 introduces a new privacy feature called Total Cookie Protection.
• Flash support was removed.
• A new printing interface was introduced in Firefox 81.
• Improved network partitioning support in Firefox 85.
• JavaScript is supported in PDF documents.

Firefox ESR is also the base of the Tor Browser. The developers of the Tor browser will update the browser to the new ESR version as well, eventually.

Firefox ESR users may want to test the new version before they upgrade existing installations and profiles. You could download and run the portable version of Firefox ESR from Portable Apps for testing; it does not interfere with the active installation, as it is portable, and you could import the Firefox profile from the installed version to the portable version to test it.  Firefox ESR versions are not upgraded automatically to a new base version, this begins with the second release after the release of the new base version.

Closing Words

The new Firefox 91 base for ESR releases introduces significant changes to various features of the browser. Some features are removed, e.g. Flash support is gone for good and the interface redesign has removed some options, but there are also new features, such as improved privacy protections. Organizations who rely on these features lose another option, and need to look elsewhere, e.g. Pale Moon, for support.

Firefox ESR 91: new ESR version will be released tomorrow