. This was the final major release to support Yosemite before Mozilla moved its minimum requirements to macOS 10.12 Sierra and later. Firefox 78.15.0esr
Select and uncheck Use a background service to install updates . Important Considerations firefox download for mac 10105 upd
The Extended Support Release channel was designed to provide long-term support for older systems. While it is no longer receiving new security patches as of October 2021 Redownload the DMG from the FTP link above
Open Firefox → Firefox menu → Preferences → → Select “Check for updates but let me choose to install them” – or better, “Never check for updates” (since newer updates will break). Go to Preferences >
| Error Message | Solution | | :--- | :--- | | “Firefox is damaged and can’t be opened” | Your download is incomplete. Redownload the DMG from the FTP link above. | | “A newer version of Firefox is already in your Applications folder” | Delete all existing Firefox instances (including subfolders). Then reinstall 78.15.0 ESR. | | *“Your browser is out of date” website warning | You cannot fix this fully. Try a user-agent switcher add-on, but many modern JavaScript functions will still fail. | | Certificate errors on major sites (Google, YouTube) | Firefox 78’s root certificates are largely expired. Go to Preferences > Privacy & Security > Certificates > Query OCSP responder servers — enable this, but expect some sites to not load. |
in the address bar to try disabling it for that specific site. Upgrade Options : If your hardware allows it, consider upgrading your OS to 10.11 El Capitan 10.13 High Sierra . High Sierra supports Firefox 115 ESR
If Firefox is already installed on your Mac, you can also update it directly from within the browser: