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).
If your hardware allows, upgrading to macOS 10.13 (High Sierra) would let you run Firefox 115 ESR , which is significantly newer and more secure. How to update outdated browser on OS X Yosemite
Whether you are looking to enhance your online privacy, enjoy the latest browser features, or simply find a fast and reliable alternative to Safari or Chrome, Firefox is an outstanding choice for your Catalina-based Mac. The browser’s robust feature set, regular updates, and commitment to open standards make it a favorite among tech enthusiasts and casual users alike.
. Users remaining on this legacy OS face significant security risks as this version ceased receiving critical security updates in October 2021. Technical Findings Last Compatible Version firefox download for mac 10105 upd
Mozilla moved users on OS X 10.9, 10.10, and 10.11 to the Extended Support Release (ESR) channel to provide a few extra years of security. However, maintaining support for decade-old operating systems became unsustainable as web technologies evolved. Mozilla Support Better Alternatives for Your Mac
Because you are on the ESR branch, Firefox will try to update to a newer ESR (like 91 or 102), which will break compatibility.
It stopped receiving security updates in October 2021. Open Firefox → Firefox menu → Preferences →
Updating to the last available version keeps your browsing experience safer for a bit longer. The Best Option: Firefox 78 ESR for Mac 10.10.5
: Older security certificates built into OS X 10.10.5 will throw security exceptions on HTTPS websites. Firefox uses its own internal certificate store, which helps bypass some of Safari's errors, but it can still drop connections on newer cryptographic layers.
Firefox Download for Mac 10.10.5: Guide to Finding the Latest Supported Version The browser’s robust feature set, regular updates, and
While this setup is not recommended for primary, secure daily driving, it is the best possible modern browsing experience available for your legacy hardware. Keep your expectations realistic, use a robust ad-blocker, and consider upgrading your machine at the earliest opportunity.
Click to download. This is the official, signed Mozilla disk image. Be wary of third-party sites claiming to offer “Firefox for Mac 10105 upd”—only download from ftp.mozilla.org for security.
: Open your current browser and go to the official Mozilla FTP Archive Server for Firefox 78.15.0esr.