Plan to move macOS 10.9, 10.10 and 10.11 users to ESR78

[Romain Testard]

Hello All,

*tl;dr:

We plan on moving macOS 10.9, 10.10 and 10.11 users to ESR78 as part of the
first step towards end of support for these platform versions.

*Goal*

Continue to provide an excellent browsing experience and ongoing security
updates to macOS 10.9, 10.10 and 10.11 users and reduce cost of supporting
these platform versions.

*Plan*

- Move macOS 10.9, 10.10 and 10.11 users to an Extended Support Release
when Firefox 78 branches

- Continue to provide security updates for the life of ESR 78 (until summer
2021)

- In summer 2021, when ESR 78 reaches the end of support, leave macOS 10.9,
10.10 and 10.11 users on the last version of ESR78 - these users won’t be
receiving security updates past this point

*Background*

While Apple doesn’t have a public policy governing security updates for
older macOS releases, their ongoing practice has been to support the most
recent three releases (i.e. version N, N-1, and N-2) - the last security
update applicable to macOS 10.11 was made available in July 2018 (
https://support.apple.com/en-us/HT201222). Unsupported operating systems
receive no security updates, have known exploits, and can be dangerous to
use, which makes it difficult to maintain Firefox on those versions.

The affected macOS versions represent 2.8M MAU with the following breakdown
(you can access details of queries related to the migration on
https://sql.telemetry.mozilla.org/dashboard/moving-macos-10-9-10-10-10-11-users-to-esr-78
):

-

OSX 10.9 548,000 MAU
-

OSX 10.10: 855,000 MAU
-

OSX 10.11 1,426,000 MAU


We feel that continuing to provide updates via ESR 78 allows us to reduce
the opportunity cost of supporting these OS versions, while keeping users
as safe as we can.

*Opportunity Cost of Supporting macOS 10.9, 10.10 and 10.11*

By removing macOS 10.9, 10.10 and 10.11 from new Firefox releases we can:

- Lower testing/operational costs

- Avoid macOS 10.9, 10.10 and 10.11 specific bugs/regressions

*What does this mean for macOS 10.9, 10.10 and 10.11 users?*

- Firefox 78 will be the last version of Firefox available to them

- They will continue to get security updates until summer 2021

*How will this plan be communicated?*

Subsequent to the collection of feedback from this email, I will be
drafting a blog post describing the finalized plan. In addition, we just
published a SUMO page (https://support.mozilla.org/en-US/kb/macos-users-esr)
describing the plans.

If you have questions/comments, please reply to the *dev-platform* mailing
list.


Thanks,

Romain

Product manager on Firefox desktop