H3M

H3M is the file extension used for map files in Heroes of Might and Magic III (HoMM3). These maps define the playable world for a scenario or campaign and are used by players to create, share, and load custom content. An H3M file encodes the layout and features of a map, including its width and height, the terrain type of every tile, and the placement of towns, mines, treasures, monsters, artifacts, and other objects. It also contains configuration data such as the number of players, starting positions, AI settings, and victory or defeat conditions, along with metadata like the map name and author.

The H3M format is primarily binary and is read by the game’s built-in map editor as well as by various fan-made tools. A range of external editors and converters exist, enabling users to design maps visually and export them as H3M or convert them to other formats. Maps created in this format can be used with the original HoMM3 release and with the HD Edition, though compatibility may vary with some third-party tools or mods.

Because of its long-standing use within the HoMM3 community, H3M maps have a robust ecosystem of shared designs, tutorials, and editing guidance. The file format is not officially documented in detail by the publisher, and much of the current understanding comes from reverse-engineering and community documentation. This has allowed a stable culture of map creation and distribution that persists across different versions of the game.