Firefox is on its last full release (currently version 115) for MacOS
10.12, 10.13, and 10.14, but is still getting security updates and will
do until September 2024. (See article below.)
Chrome and Brave are also dropping support for these older versions of
MacOS. :-(
Chromium Legacy is one of the few (only?) web browsers still being
updated for older versions of MacOS.
<
https://github.com/blueboxd/chromium-legacy/releases>
The web browsers themselves will of course still work, although the
number of websites that don't work properly will slowly grow. I've
noticed it already happening in MacOS 10.13 Safari, but so far it is
only a couple of websites that I only occassionally use.
Firefox support for macOS 10.12, 10.13 and 10.14
------------------------------------------------
July 6, 2023
With Firefox 115, users on macOS 10.12 (Sierra), macOS 10.13
(High Sierra) and macOS 10.14 (Mojave) will automatically be
moved to the Firefox Extended Support Release (ESR).
While Apple doesn’t have an official policy governing security
updates for older macOS releases, their recent practice has
been to support the most recent three releases. The last
security update for macOS 10.14 was nearly two years ago in
July 2021. Moving users to the ESR 115 version of Firefox will
allow Mozilla to continue providing security updates until at
least September 2024. Users do not need to take additional
action to receive these updates.
We strongly encourage users to upgrade to a version of macOS
that is supported by Apple. When migrating to a new device,
users can use a Firefox Account to easily keep all of their
settings, ensuring all bookmarks, browsing history and saved
passwords are immediately available after installing Firefox.
Unsupported operating systems receive no security updates and
can be dangerous for you to use. For planning purposes,
enterprises using Firefox should consider September 2024 as
the support end date for macOS 10.12, 10.13 and 10.14.
<
https://blog.mozilla.org/futurereleases/2023/07/06/firefox-support-for-macos-10-12-10-13-and-10-14/>