ESR is short for Extended Support Release channel. The channel has been made more for Enterprise users in mind as they like longer term stability with security/stability fixes vs having latest Release. Mozilla however has used ESR versions to help support EOL OS's for a while longer, a lot longer compared to when Chrome/Chromium browsers dropped support. Since it appears you are using the old EOL Windows 7 the latest version you can run is Firefox 115 ESR currently at Fx 115.29.0 and is planned for updates until Fx 115.33.0esr in February 2026 unless updates are extended yet again. Firefox 116.0 and later requires Windows 10, 11 to run. https://support.mozilla.org/en-US/kb/firefox-users-windows-7-8-and-81-moving-extended-support Firefox 115.29.0esr was released Oct 14, 2025 as to why there is an update prompt if you have 115.28.0esr or earlier. https://www.firefox.com/firefox/115.29.0/releasenotes/ https://www.firefox.com/releases/