Minecraft structure block file format
Minecraft structure block file format is a data format used in the Java Edition of the Minecraft game. This and other Minecraft formats are extensively documented in the Minecraft Gamepedia wiki.
The format is used (within the client.jar file) to represent structures such as end city, igloo, fossil, and custom structures. The third-party Schematic file format is similar to it. The format used is the Minecraft NBT format.