To run version 91.2.0, Windows users need Windows 7 or newer, while Mac users need macOS 10.12 or newer. Important Support Information
While this version is no longer the current ESR, it can still be found through official Mozilla archives. It is highly recommended to only use official sources to avoid malware. firefox 91.2.0 download
The ESR (Extended Support Release) channel is preferred for: To run version 91
While version 91.2.0 was focused on stability and security, it carried forward major improvements introduced in the broader Firefox 91 cycle: To run version 91.2.0
Avoiding the frequent UI changes of the standard rapid-release channel.
Embedded JavaScript in PDF files was enabled for better form functionality.