Minecraft NBT format
Minecraft NBT format is a data format used in the Minecraft game as the underlying format of various Minecraft data formats such as the Minecraft Anvil format. This and other Minecraft formats are extensively documented in the Minecraft Gamepedia wiki.
NBT (Named Binary Tag) is a binary file format consisting of data in a tree structure made up of tags. There is also a text-based "stringified NBT" format. This is different from JSON, but uses parts that are in JSON format.
Version 19132 was the earliest known version, introduced in Beta 1.3, while version 19133 is a later revision used in the Anvil format, adding the Int Array tag.