Contra: Hard Corps has significant differences between the Japanese, American, and European versions. In the Japanese version the characters all have a lifebar, and can be hit three times. This version also has unlimited continues unlike the American and European (PAL) version. The American and European version does not have a lifebar; a single bullet will take a life. This makes the American and European version significantly more challenging.

The European version also has significant censorship. The game is called Probotector and all the characters in the game are robots. Furthermore the plot and cut-scenes are different. The antagonists are aliens and the Alien Cell's name was changed to the "X-Drive".