If your MacOS is older than 10.12, see this article. https://support.mozilla.org/en-US/kb/firefox-mac-osx-users-esr

''<p>reggie1x [[#question-1383624|said]]</p>'' <blockquote>If Current Mac System Is Older How to obtain an older version of Firefox. </blockquote> Firefox since Fx '''79.0''' and later including the current Fx 102 and Fx 102 ESR requires Mac OS X '''10.12''' (ten.twelve) at minimum. Besides updating your OS to Mac OS X 10.'''12''' or later, the most current Firefox version you can install on older macOS is Fx '''78.15.0''' ESR though it is EOL with no more updates. ESR stands for Extended Support Release and was meant more for Enterprise users in mind as they like stability. https://support.mozilla.org/en-US/kb/firefox-mac-osx-users-esr https://www.mozilla.org/firefox/78.0/system-requirements/ https://www.mozilla.org/firefox/79.0/system-requirements/ https://www.mozilla.org/firefox/102.0/system-requirements/ '''In case you ever need the Firefox 78.15.0esr file''' see below links. https://archive.mozilla.org/pub/firefox/releases/78.15.0esr/mac/en-US/ other locales at https://archive.mozilla.org/pub/firefox/releases/78.15.0esr/mac/