The Ultimate Guide: Firefox Download for Mac 10105 Upd – How to Get the Latest Version on Older macOS Systems

Published: May 2026
Reading Time: 6 minutes

If you’ve searched for “firefox download for mac 10105 upd” , you are likely running an older Mac – specifically one capped at macOS 10.10.5 (Yosemite) or a similar legacy build (e.g., 10.11, 10.12). The “upd” in your query suggests you need the latest possible update for that environment.

Apple no longer supports OS X Yosemite, but Mozilla has historically provided extended support releases (ESR) for older Macs. This article will walk you through exactly how to find, download, install, and troubleshoot Firefox for Mac OS X 10.10.5, ensuring you get the final secure update available.

Why Standard Firefox No Longer Works on 10.10.5

Mozilla regularly updates Firefox to include new web standards, security protocols, and performance optimizations. However, modern software requires modern operating system foundations.

If you attempt to install a newer Firefox (version 80 or above) on 10.10.5, the installer will fail. You need the legacy build.

What is Firefox ESR?

ESR stands for Extended Support Release. This is a version of Firefox intended for schools, universities, and businesses that need a stable browser for longer periods. While standard Firefox updates every few weeks with new features, ESR updates less frequently and focuses strictly on security patches.

5. Installation Steps (Detailed)

  1. Mount the DMG – opens a Finder window with Firefox icon.
  2. Drag Firefox to Applications folder – not to Desktop.
  3. Open Applications → right-click Firefox → Open (first launch bypasses Gatekeeper).
  4. If macOS says “unidentified developer”:
    • Hold Control + click Firefox → Open → confirm.
  5. Disable automatic updates immediately:
    • Firefox menu → Preferences → General → Never check for updates.