While Firefox 52.9.0 ESR is the most stable option for Vista, there are critical risks to keep in mind: Installation and updates | Firefox Help - Mozilla Support
: Even if you have a 64-bit version of Windows Vista, you must use the Windows 32-bit (Win32) installer. The 64-bit builds of Firefox require Windows 7 or later. download mozilla firefox for windows vista
Mozilla officially ended support for Windows Vista in . The final version that works on this system is Firefox 52.9.0 Extended Support Release (ESR) . How to Download Firefox for Windows Vista While Firefox 52
To download for Windows Vista , you must use a specific legacy version, as modern versions of the browser are no longer compatible with this operating system. The final version that works on this system is Firefox 52
: Once downloaded, open the .exe file and follow the standard installation prompts. Important Security & Compatibility Notes