Locate the downloaded file in your folder and double-click it.
If that’s the case, here’s a full feature guide on downloading and running on macOS 10.10.5 , including compatibility, risks, and step-by-step instructions.
| Update Method | How It Works | Best For | | :--- | :--- | :--- | | | Firefox checks for, downloads, and installs updates in the background when you restart the browser. | Most users who want a seamless, hands-off experience. | | Manual Download & Install | You visit the official Firefox website, download the latest installer, and run it to overwrite your current version. | Users who want immediate control over when an update is installed, or who are troubleshooting update issues. |
Using a legacy browser presents distinct challenges. Because version 78.15.0esr stopped receiving updates, you may encounter rendering bugs and security warnings. Dealing with Broken Websites firefox download for mac 10105 upd
If your underlying hardware structure supports a cleaner upgrade path, staying on Yosemite 10.10.5 is heavily discouraged due to open network exploits.
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.
To avoid corrupted packages or malware from untrusted mirror portals, you must source this specific version directly from Mozilla's historical server distribution network. Locate the downloaded file in your folder and
Select the , which will end with the .dmg file extension (e.g., Firefox 78.15.0esr.dmg ).
Downloading Firefox for Mac OS X 10.10.5 Yosemite: The Complete Guide
If your hardware allows, it is highly recommended to update your macOS to a newer version (10.15 or later) to use the latest, most secure version of Firefox. | Most users who want a seamless, hands-off experience
If you attempt to click the primary download button on the official Mozilla Firefox Page , your system will fetch a modern .dmg installation package designed for modern macOS builds. Opening this modern package on OS X 10.10.5 will result in a visual error block or a crossed-out application icon signaling that your operating system version is unsupported.
Disclaimer: Using unpatched browsers on older operating systems carries inherent security risks. Always back up your data. If you'd like, I can: Tell you directly.