Firefox Legacy is an unofficial modified version of Mozilla Firefox that works on Mac OS X 10.6 Snow Leopard.
Download it now and breathe new life into your old Mac.
As of 2021-10-24, Firefox Legacy is no longer supported. It has become increasingly challenging to update it to a more modern Firefox version, and I no longer use it myself.
There will be no further updates to Firefox Legacy.
For an up-to-date browser for older Macs, try Chromium Legacy. You may need to open this direct link in Firefox Legacy to download Chromium Updater; no other browser for OS X 10.7-10.8 is able to display GitHub correctly. When opened, Chromium Updater will appear as an icon on the right side of the menu bar. Click it, then select a stable version of Chromium Legacy to download. Once the new copy of Chromium Legacy is downloaded, drag it to the Applications folder. You can keep Chromium Updater and use it to update the installed copy of Chromium Legacy.
To enable Google sync in Chromium Legacy, quit the browser, then enter the following command in Terminal (it is one long line):
open -a /Applications/Chromium.app --args "--oauth2-client-id=77185425430.apps.googleusercontent.com --oauth2-client-secret=OTJgUOQcT7lO7GsGZq2G4IlT"Chromium Legacy will open; log into your Google account. You will not need to run the command again unless you log out.
Firefox Legacy for OS X 10.7 Lion and 10.8 Mountain Lion is no longer available for download because it offers no advantages over Chromium Legacy.
If you only need to use Firefox Legacy as a stepping stone to download a newer browser, the 10.6 version will work on 10.7 and 10.8.
Only Firefox 52.9.1 is available for OS X 10.6 Snow Leopard; it will receive no further updates, in part due to technical limitations of the OS.
Note: the program is called "Nightly" due to licensing restrictions prohibiting the use of the official Firefox branding.
Final version for OS X 10.6 Snow Leopard: 52.9.1p1 (2020-04-11)
Any of the language packs for the matching official Firefox version are supported.