It looks like you have the old eol macOS 10.10 For macOS 10.9, 10.10, 10.11 the most current Firefox version you can run is Firefox 78.15.0esr. https://support.mozilla.org/en-US/kb/firefox-mac-osx-users-esr Firefox 79.0 to 115 ESR requires macOS 10.12, 10.13, 10.14 to run. Firefox 116.0 and later requires macOS 10.15 or later to run. https://support.mozilla.org/en-US/kb/firefox-users-macos-1012-1013-1014-moving-to-extended-support