Alternative Option: Modernizing Yosemite with Firefox Dynasty
Before installing, check that your Mac hardware aligns with these legacy requirements: Specification Mac OS X 10.10.5 (Yosemite) Exact Software Version Firefox 78.15.0esr File Format Apple Disk Image ( .dmg ) Architecture Intel 64-bit Last Security Update October 5, 2021 Managing Performance and Limitations on OS X 10.10.5
: Double-click the downloaded file to open the installer window. : Drag the Firefox icon Applications folder firefox download for mac 10105 upd
For users running , downloading the latest version of Mozilla Firefox directly from the main website will not work. Modern versions of Mozilla Firefox require macOS 10.15 (Catalina) or later.
Because standard download pages automatically offer the newest version (which requires macOS 10.15 or later), you must access Mozilla’s archives directly to find the compatible file: A: YouTube will work in basic HTML5 mode (480p/720p)
: Ensure you haven't accidentally downloaded a newer version. Check the version by selecting About Firefox in the menu. "Up to Date" Messages
, which remained supported with security updates much longer. as these are vectors for malware.
A: YouTube will work in basic HTML5 mode (480p/720p). Netflix will likely fail because Widevine DRM on Firefox 78 is too old to validate current licenses.
Do not download Firefox from random "free software" sites, as these are vectors for malware.