Firefox ESR

Mozilla Firefox Extended Support Release

A community-led project that allows organizations to benefit from the speed, flexibility and security of Firefox while getting the support they need.

Firefox Extended Support Release (ESR) is intended for system administrators who deploy and maintain the desktop environment in organizations such as universities and other schools, county or city governments and businesses.

We encourage those who are deploying Firefox ESR to sign up for the Mozilla Enterprise mailing list available in English, French and German. This list is a great place to discuss deploying Firefox with other community members. Regular communications regarding product updates and support are also sent on the list by various Mozilla teams.


What is Mozilla?

Mozilla is a global, non-profit organization dedicated to making the Web better. We emphasize principle over profit, and believe that the Web is a shared public resource to be cared for, not a commodity to be sold. We work with a worldwide community to create open source products like Mozilla Firefox, and to innovate for the benefit of the individual and the betterment of the Web. The result is great products built by passionate people and better Web choices for everyone. For more information, visit

What is Mozilla Firefox ESR?

Mozilla will offer an Extended Support Release (ESR) based on a regular release of Firefox for desktop for use by organizations including schools, universities, businesses and others who need extended support for mass deployments.

Where can I download Mozilla Firefox ESR?

You can download Mozilla Firefox ESR here.

What does the Mozilla Firefox ESR life cycle look like?

Releases will be maintained for more than a year, with point releases containing security updates coinciding with regular Firefox releases. The ESR will also have a two cycles (12 week) overlap between the time of a new release and the end-of-life of the previous release to permit testing and certification prior to deploying a new version.

Mozilla relies on Firefox ESR users to provide feedback for the new ESR releases. During the first two cycles, please report any bugs about web compatibility regressions, stability issues, and so on.

Maintenance of each ESR, through point releases, is limited to high-risk/high-impact security vulnerabilities and in rare cases may also include off-schedule releases that address live security vulnerabilities. Backports of any functional enhancements and/or stability fixes are not in scope.

At the end of the support period for an ESR version:

  • the release will reach its end-of-life
  • no further updates will be offered for that version
  • an update to the next version will be offered through the application update service

You can read more about the plan here.

Firefox ESR Release Overview

Who should use Mozilla Firefox ESR?

Mozilla Firefox ESR is meant for organizations that manage their client desktops, including schools, businesses and other institutions that want to offer Firefox. Users who want to get the latest features, performance enhancements and technologies in their browsing experience should download Firefox for personal use, as these improvements will only be available to ESR users several development cycles after being made available in Firefox for desktop. If you’re using Firefox for personal use, you can download Firefox from

In some cases, ESR is proposed to regular users for unsupported architectures transition. For example, when Windows XP support ended for the release, Firefox ESR has been recommended for these users.

What does my organization need to do to use Mozilla Firefox ESR?

System administrators who deploy Firefox ESR are encouraged to sign up for the Enterprise mailing list and test Beta versions of Firefox and ESR Release Candidates. You can also file bugs for issues you may encounter here or follow known bugs here.

How can I learn about the latest Mozilla Firefox ESR news?

To learn about the latest Mozilla Firefox ESR news, administrators are encouraged to subscribe to the Mozilla Enterprise mailing list available in English, French and German. This is where Mozilla communicates the latest information about Firefox ESR and other product updates.

What is the Enterprise mailing list?

The Mozilla Enterprise mailing list run by the Mozilla Enterprise User Working Group (EWG) is where enterprise developers, IT staff, and Firefox developers discuss best practices for deploying Firefox in the enterprise.

Where can I get technical support for Mozilla Firefox ESR?

Mozilla Firefox ESR support can be found through the mailing list. As Firefox ESR is (almost) functionally identical to Firefox for desktop, users will be able to find relevant support articles here.

Is there any difference between Firefox and Firefox ESR?

Firefox and Firefox ESR are extremely similar. Rarely, some features are disabled in ESR for different reasons like stability issues, potential changes in the specifications, etc. Any differences between the regular release and ESR are documented in the release notes of the first ESR release of the cycle.

How do I customize Firefox to meet my organization’s IT policy/requirements?

There are several methods that can be used to customize Firefox and the best place to start is the Enterprise list or the enterprise deployment article on MDN. There is also an add-on for administrators as well as third-party organizations who provide customization services, and the Enterprise list is a good place to discuss requirements if you’re just getting started.

Does Mozilla provide an upgrade path between two ESR versions?

Yes, an ESR will be automatically upgraded to the subsequent ESR. System administrators can disable automatic updates by managing ESR through their deployment system. From a major version to the other (example: the 45 to 52 migration), the updates will be proposed only after the X.2.0 version is released. For example, users of 45 have been updated only when 52.2.0 has been published.

Is Mozilla Firefox ESR available in my language?

Firefox ESR is available in every locale currently available for Firefox. Because of the precise needs of ESR, it’s encouraged for system administrators deploying the build to register and participate in an mailing list. This is only available in English, French and German, but if you would like to volunteer to lead an Enterprise mailing list in your language, please get in touch.

How can I unsubscribe from the mailing list?

Visit your language’s mailing list linked above and fill the unsubscription form at the bottom of the page, or send an email to the list moderator as instructed at the bottom of each post.

Is Mozilla Firefox ESR available for Android and iOS?

No. Firefox ESR will only be offered for Windows, macOS and Linux for desktop computers.

Does Mozilla Firefox ESR work with any website?

Generally speaking, yes. However, it should be noted that some web applications including popular SaaS like G Suite and Office 365 only support the latest Firefox release. If your organization is using one of those applications, please consider deploying the latest release instead of ESR to meet the requirements.