Files with the .FCM extension contain saved three-dimensional world maps for navigation, for use by Minecraft Classic players.

The FCM format is used by the servers of producers other than of the game. The format was created for the purposes of fCraft servers, which support multiplayer worlds in the Minecraft Classic video game. The maps, saved in the FCM format, are hosted on those servers and saved in the map catalog. The format is also used by servers from the Spacecraft family.