Version 78 ESR is the latest for MacOS 10.10. We don't provide updates for 10.10 anymore, you have to update your OS first.

/moved thread from Firefox for iOS (for iPhone/iPad) to Firefox section as you have macOS. For the old macOS 10.9, 10.10, 10.11 the most current Firefox 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 at minimum to run while Firefox 116.0 to current 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 If you hardware does support updating your macOS to at least 10.12 then you can run Firefox 115 ESR which is currently at 115.18.0esr and will be updated to 115.21.0esr in March 2025. Mozilla will decide in early 2025 on whether to extend 115 ESR updates again.