hi, you can set a custom install path for firefox when you do a custom installation. however, if you'd put your programs onto the SSD you'd get the most performance gains out of it!

i just had to warranty replace my SSD so i am trying to reduce writes to it as much as possible,thank you for your reply.

If you use the custom installation option on the the first installation screen, you can install Firefox anywhere you want. But that's just for the Program Files, your Profile folders will default to the users - Local and to users - Roaming folders on the same drive where your Operating System is installed. You can create a new Profile wherever you want, but the process is fairly advanced, it can slow things down as philipp mentioned, and there can be minor issues with it for less experienced users.

See if you can figure out the 3 locations that Firefox uses for its files /folders. Program Files Profile folder Cache - 2ndary Profile folder