If macOS prevents the app from opening, go to and click Open Anyway . Critical Support Information How to update outdated browser on OS X Yosemite
If you need a different language, navigate the Mozilla FTP directory to find your specific locale folder. : firefox download for mac 10105 upd
If Firefox 78 does not meet your needs, some users on legacy macOS versions look toward community-maintained browsers like Pale Moon or SeaMonkey , though compatibility varies. If macOS prevents the app from opening, go
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If you try to install a newer Firefox (version 100+), the installer will fail with an error: “You cannot use this version of Firefox with this version of macOS.”
: You can download this specific legacy version directly from the Mozilla FTP Archive. How to Install