Latest news. Due to ongoing popularity of these old macOS releases, Firefox ESR 115 has been extended to September 2025:
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Yay for the old 2012 MBP’s Mojave v10.14.6 with Firefox ESR!
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Ditto for my Mid-2011 iMac maxed out at 10.13.6.
Good news. It’s been extended another six months, to March 2026:
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Great! My Mid-2011 iMac is maxed out at MacOS 10.13.6. Hmm, I wonder if this means I can go past Firefox ESR 115.27 to 115.33?
EDIT: Apparently not as I’m offered only 115.27
I love this! Still on Mojave and High Sierra on machines that need to run certain older apps.
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I don’t see why not.
Ummm… 115.27 is the latest 115 ESR build.
115.28 will be released next week, on September 16.
115.33 won’t be released until February 24th.
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Ah, OK. I saw a list but thought the 28 through 33 were releases that had been for the 10.14, 10.15, 11, and 12 versions.
I’m not sure if I’ve seen it mentioned on TidBITS, but Mozilla has extended Firefox 115 ESR support for macOS 10.12-10.14 and Windows 7/8 through at least August 2026. This is good news, but keep in mind that the ESR stream includes security patches, but generally does not include other bug fixes or new features. As others have noted, Firefox 115 ESR is three years old and does have trouble rendering some websites.
We have decided to extend support to ESR 115 only on Windows 7-8.1 and macOS 10.12-10.14 up to August 2026 . We will re-evaluate this decision in July 2026 and announce any updates on ESR 115’s end-of-life then.
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Back when I was still working with my old 2012 MacBook Pro running OS X 10.8 Mountain Lion, once Firefox and then Firefox ESR were no longer compatible, I switched over to Waterfox and then to Waterfox Classic, both of which ran pretty well. Waterfox and its older Classic version are still options for those of us who can no longer run the current versions of Firefox.
Note that (from the Waterfox download page) the current version (6.6.13) requires macOS 10.15 (“Catalina”) or later. I don’t know if there is a way to download or get information about older versions.
I’m not sure what the requirements for Waterfox Classic are, but the main page says that there are many unpatched security advisories, and its last release was in November 2022, so exercise caution with this one.
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What’s a Firefox “ESR”?
ESR = Extended Support Release
The “ESR” is a special, officially supported version of Firefox that gets security fixes and bug fixes, but not new features. Further, it is maintained much longer than the standard “rapid release” version of Firefox. The ESR is aimed at organizations and end users that value stable features over time, rather than rapid introduction of new features.
More detail:
Mozilla maintains several official “branches” of Firefox. Most people use the “Rapid Release” branch. The Rapid Release branch is the officially supported version of Firefox that is intended for general use. There is a new Rapid Release of Firefox roughly every four weeks. Each Rapid Release includes new features, and it usually gets one or more incremental security and bug fix updates before the next general release.
For example, as I write this, the current version of Firefox is 151.0.2, which is the second incremental update to the version 151 Rapid Release. Version 151 was released on May 19, 2026, and version 152 is scheduled to be released on June 16th.
In contrast, a new ESR version is released roughly once every thirty weeks to a year and is based on the general release at the time.
For example, the current ESR is version 140.12esr, based on Firefox Rapid Release 140. You can think of it as a specially maintained version of Firefox 140 that is still receiving security patches and selected bug fixes, but no new features. The next ESR, version 153, will incorporate the features added between Rapid Release 140 and Rapid Release 153. It is scheduled to come out in July.
When Firefox drops support for an operating system in its Rapid Releases, ESRs can be of special interest for users of the dropped operating system, since they end up being supported longer than the Rapid Release versions. For example, Firefox 115 ESR is a very unusual ESR release that is still supported three years after its release. It is maintained specifically to support macOS 10.12 through 10.14 and Windows 7 and 8.1. Support for 115 ESR is scheduled to expire in August 2026, though Mozilla has indicated that it may decide to extend support beyond that date.
Edited to use “Rapid Release,” which is Mozilla’s term for the standard/general version of Firefox. Edited again to add a link, reword a thing or two for clarity, and to fix a typo.
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I have installed Firefox ESR for a number of people who cannot or will not upgrade to the “current” macOS (and can thus run the latest Firefox version).
The fact that Mozilla has continued to patch ESR 115 is amazing. Mostly this is due to the volume of Windows 7 and 8.1 users, but macOS 10.12 thru 10.14 benefit as well. You can check their notices about ESR 115 here:
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I agree. I’m also impressed that they still maintain the Rapid Release version on Catalina!
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