Minecraft Anvil format
From Just Solve the File Format Problem
Minecraft Anvil format is a data format used in the Java Edition of the Minecraft game, superseding the Minecraft Region format (and before that the Minecraft Alpha level format). This and other Minecraft formats are extensively documented in the Minecraft Gamepedia wiki.
Changes from the Region format consisted of changes to the Minecraft chunk format used within it. (This format, in turn, uses the Minecraft NBT format.)
