GS0 is an extension characteristic of programs emulating older game consoles called Sega Genesis (Megadrive). GS0 are files used to store the state of the game. In this way, the user can continue the game from the moment of saving the game. It is not necessary to start the game from the beginning.

The progress of the game in Sega Genesis console emulators can be saved in 10 files with the extension from GS0 to GS9. Popular emulators of this console include, among others, Genecyst or Kega Fusion.