To update or download Mozilla Firefox for a Mac running , the absolute latest compatible version you can install is Firefox 78.15.0esr (Extended Support Release) . Modern, mainline releases of Firefox will not install or run on this legacy operating system, as they require macOS 10.15 Catalina or newer.
You may encounter "Your connection is not private" or certificate errors on modern websites because the browser's built-in security certificates are outdated.
, it remains the most functional official version for your OS. Where to Download: You can find older versions in the Mozilla release archives or through reputable community repositories like the Macintosh Repository How to Install Download the DMG: Locate the installer for Firefox 78.15.0esr. Open the File: Double-click the downloaded Drag to Applications: Drag the Firefox icon into your Applications Confirm the Version: Open Firefox, go to the top menu, and select Firefox > About Firefox to ensure you are on version 78. Critical Security Warning firefox download for mac 10105 upd
: Using Firefox 78 ESR means no new features, and security updates ended in 2021. For better security, consider updating macOS (if your Mac supports it) or switching to a lightweight browser like Pale Moon or Arctic Fox (community-maintained for older macOS).
Because Firefox 78 ESR stopped receiving security updates in late 2021, it is vulnerable to modern web exploits. For a more secure experience on Yosemite, consider these alternatives: How to update outdated browser on OS X Yosemite 3 Sept 2024 — To update or download Mozilla Firefox for a
Over time, web architectures have changed. Older operating systems lack the core system APIs needed to run today’s web engines.
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. , it remains the most functional official version
Open your current browser (even Safari 11) and navigate to:
Firefox Download for Mac 10.10.5 Update: The Complete Legacy Installation Guide
: If macOS blocks the app because it's from an "unidentified developer," go to System Preferences > Security & Privacy Open Anyway Mozilla Support Troubleshooting Tips If Firefox Won't Open
Navigate to the official Mozilla FTP archive or the Mozilla Support page for legacy systems . Download the file named Firefox 78.15.0esr.dmg . : Open the downloaded .dmg file from your Downloads folder. Drag the Firefox icon into your Applications folder.
