Slot Data

The Slot data structure is how Minecraft represents an item and its associated data in the Minecraft Protocol.

Slot

Name	Type	Meaning
Present	Boolean	True if there is an item in this position; false if it is empty.
Item ID	Optional VarInt	Omitted if present is false. The item ID. Item IDs are distinct from block IDs; see Data Generators for more information
Item Count	Optional Byte	Omitted if present is false.
NBT	Optional NBT	Omitted if present is false. If 0 (TAG_End), there is no NBT data, and no further data follows. Otherwise the byte is the start of an NBT blob as shown below:

  COMPOUND
    LIST 'StoredEnchantments'
      COMPOUND
        STRING 'id'
        SHORT 'lvl'
      END
      COMPOUND
        ...
      END
      ...
    END
    INT 'Unbreakable'
    ...
  END

Note that on old versions, the enchantment id was sent as a SHORT, and not as a STRING.

Since 1.20.2 the root compound also has no name anymore. The NBT data starts with one byte indicating the type, followed by the type-specific data.

See NBT for more information about the NBT format, and here for the contained information and its format. Note that tool durability is included in NBT, among other things.

Examples

  00                            | empty slot
  01 01 01 00                   | a stone block
  01 01 01 03 00 00 12 34 56 78 | a stone block with (made-up) NBT data