Download the installer and verify the file hash if provided. Method 3: Firefox Extended Support Release (For Enterprise) If you need a "stable old version" that still gets security patches, use ESR. While not "ancient," ESR is ~1 year behind the main release.
Find your desired version number (e.g., 115.0 , 91.0 , 52.0 ). Click on it. download mozilla firefox old version
Go to a trusted old-software repository. Download the installer and verify the file hash if provided
Search for "Firefox" and your target version. use ESR. While not "ancient
Search for "Firefox ESR download."
Go to the official directory: https://ftp.mozilla.org/pub/firefox/releases/