Modern versions of Mozilla Firefox require macOS 10.15 (Catalina) or later. If you attempt to download the standard, current version of Firefox from the main Mozilla homepage, the installation will fail. Your Mac will display an error message stating that the application requires a newer version of macOS.
See if your Mac can be updated to at least macOS 10.15 (Catalina) or higher.
: Standard modern builds on the Firefox Mac Download Page require macOS 10.15 Catalina or newer. How to Download and Install Firefox 78.15.0esr
Even though Firefox generally runs smoothly on macOS 10.15, you may encounter occasional issues. Here are some common problems and their solutions. firefox download for mac 10105 upd
Because this software environment stopped receiving standard updates in late 2021, you will encounter immediate structural hurdles when rendering modern websites.
As of 2026, finding a "Firefox download for Mac 10.10.5" requires focusing on specialized Extended Support Release (ESR) versions or community-maintained projects, as standard, modern Firefox no longer supports this OS.
A: No, it requires macOS 10.12+. No reliable upd exists. Modern versions of Mozilla Firefox require macOS 10
Mozilla Firefox no longer officially supports macOS 10.10.5 (Yosemite) with its current releases. The final official version compatible with this operating system is Firefox 78.15.0esr (Extended Support Release)
The latest and final version of Firefox that works on Mac OS X 10.10.5 is Firefox 78 Extended Support Release (ESR) Mozilla Support Current Status
A: Reasonably safe for non-sensitive browsing, provided you do not log into critical accounts. It is safer than Safari 10 (which is fully broken on Yosemite) or Chrome 87 (also deprecated). See if your Mac can be updated to at least macOS 10
Many Mac users find themselves in the situation where their hardware cannot be upgraded to a newer version of macOS beyond Catalina. If you are using an older Mac that is limited to macOS 10.15, you can rest assured that Firefox will still support your operating system for the foreseeable future. Mozilla has made a commitment to maintaining compatibility with Catalina, giving you access to the latest security updates, privacy features, and browser innovations.
Running Firefox 78.15 in 2026 means for Firefox-specific vulnerabilities (CVEs after Nov 2021 are unpatched). However:
If you are running an older macOS version like 10.12, the Firefox site correctly recognizes this and provides the last supported version for your system (Firefox 115 ESR).
Alternative Option: Modernizing Yosemite with Firefox Dynasty
Instead, the most recent and secure version available for your system is . Why You Need a Specific Version