What is .JST file?
Save file created and used by Jnes, a Nintendo Entertainment System (NES) emulator for Mac and Android; contains a save state of an NES game.
The JST file is the default save state used by Jnes. The emulator also uses the ".js0" to ".js9" extensions for the other 10 save slots that it supports. All save states are located in the \saves subdirectory of Jnes. If you move them from this location Jnes will not read them.
Recommended Software Programs to open .JST file