Mac OS 10.9-10.11 Firefox users will be migrated to Firefox ESR 78
Mozilla plans to release the next major ESR version of Firefox, Firefox 78, on June 30, 2020. A new major version upgrades Firefox's Extended Support Release from an older version, in this case from Firefox ESR 68, to a new version.
Firefox ESR is updated as frequently as Firefox Stable but the core difference is that Firefox ESR versions won't receive all the changes of Firefox Stable releases. These changes are pushed to Firefox ESR when a new major version is released.
Current versions of Firefox are compatible with Windows, Mac OS, and Linux. On Mac OS, Firefox is compatible with Mac OS 10.9 to Mac OS 10.15 and users may install any Firefox channel on these devices.
The release of Firefox 78 and Firefox ESR 78 changes that. Mozilla plans to end support for Mac OS 10.9 to 10.11 (Mac OS X Mavericks, Yosemite, and El Capitan) next year; Firefox Stable installations on these systems will be migrated to Firefox ESR 78 when the new version is released on June 30, 2020.
Why is that done? Mozilla notes on Bugzilla:
We currently support macOS versions 10.9 to 10.15. We're looking at moving users on versions < 10.12 to the esr branch with the release of Firefox 78, to both be able to support them for about a year longer, and reduce the burden from old versions on engineering and QA for mainline Firefox.
A meta bug has been created on Bugzilla that tracks the migration process. Mac OS X users of Firefox who still use these older versions of the Mac OS X operating system will be able to use Firefox ESR for another year before support runs out. It is unclear if and how other Firefox channel installations, e.g. Firefox Nightly or Beta, are affected by Mozilla's decision to end support.
Firefox ESR 78 won't receive new feature updates but will receive bug fixes and security updates. Mozilla's Hardware dashboard provides no details on the soon to be retired Mac OS X versions; these are likely filed under macOS Other and had a share of 2.2% in February 2020. Note that the stat includes all Mac versions except for Catalina, Mojave and High Sierra.
Google Chrome's current system requirements on Mac require OS X Yosemite 10.10 or later.
Closing Words
I could not find exact Mac OS usage figures but the decision will certainly impact some Firefox users. Mozilla has not shut out users from installing Firefox on unsupported systems in the past but these don't receive support from the company and bugs specific to these systems won't be fixed either.
With Mozilla's market share not looking that rosy, I'd expect the company to retain users whenever possible even if that means supporting older operating system versions. The organization has all the figures at hand to make an educated decision on the other hand. (via Sören)
I wonder when Windows 7 users will also be transitioned onto an ESR release? No news yet from Mozilla about when Win7 support will drop (though Chrome and the new Microsoft Edge both end July 15, 2021)
I am quite sure that it’s not only business-wise but also, user-friendly wise (Think Hackintosh, the bridge to other stand-alone o.s. system and also dual boot systems) and most important I personally convinced that especially community-wise, its not a so smart decision.
@Paul(us)
Do you really expect the Hackintosh to survive Apple‘s ongoing rollout of the T2 chip? The Hackintosh community is finished, they just don‘t know it yet.
Let’s hope that Mozilla made a thorough analysis of the pros and cons.