What Firefox version is the bank saying it needs at minimum as Chase and Citi for example recently made it so Firefox 128.0 is the minimum. To run Firefox 116.0 and later including Fx 145.0.2 release and Fx 140.5.0esr requires macOS 10.15 (ten.fifteen) at minimum. https://support.mozilla.org/en-US/kb/firefox-users-macos-1012-1013-1014-moving-to-extended-support If you cannot update your macOS to 10.15 or later then you can try to change your Firefox version number to fool the bank site. # In a new tab, type or paste '''about:config''' (with a colon) in the location (address) bar and press Enter/Return. Click the button accepting the risk. # In the search box in the page, type or paste forceVersion and pause while the list is filtered # Double-click the ''network.http.useragent.forceVersion'' preference to display an editing field, and change the value to '''128''' or '''140''' to try then press Enter/Return or click the blue check mark button to save the change.