Inventory

Minecraft displays the player inventory differently, according to how the window was opened. Ranges of slot indices vary in meaning between different “windows”. The Open Inventory packet indicates which window is being opened according to:

Window Type	Description
minecraft:chest	Chest, large chest, or minecart with chest
minecraft:crafting_table	Crafting table
minecraft:furnace	Furnace
minecraft:dispenser	Dispenser
minecraft:enchanting_table	Enchantment table
minecraft:brewing_stand	Brewing stand
minecraft:villager	Villager
minecraft:beacon	Beacon
minecraft:anvil	Anvil
minecraft:hopper	Hopper or minecart with hopper
minecraft:dropper	Dropper
EntityHorse	Horse, donkey, or mule

The slot number is calculated starting at 0, counting up through the window's unique slots, and then counting through the players inventory. The number of unique slots in the window is in the Open Window (Play, 0x2d, clientbound) packet for all window types except the default inventory window, in which the number of unique slots is 9 (10 in the 1.9 snapshots). This means the slot in the upper-left corner of the player's inventory is slot n where n is the number of unique slots. Slot number -999 is used for clicking outside the window.

Rectangular regions are always indexed starting with the upper-left corner and scanning across rows. If a window has a crafting region, the output slot is always slot 0 followed immediately by the input region.

Each window type is described in the following sections. All slot index ranges are inclusive and reflect the indices observed in the Minecraft protocol.

For the window properties (additional data in each window, e.g. smelting progress or enchantments), refer to the table in the Window Property packet.

Inventory

Inventory slots

This is the inventory window that the player can always open, typically by pressing E since Beta 1.4. Before, you had to press I.

Slot range	Description
0	crafting output
1–4	2×2 crafting input (1 + x + 2 * y)
5–8	armor (head, chest, legs, feet)
9–35	main inventory
36–44	hotbar

Note that this is different from inventory items stored in a player.dat file. This may help: https://gist.github.com/459a1691c3dd751db160

Crafting table

This is the window that is opened when the player right-clicks on a workbench.

Slot range	Description
0	crafting output
1–9	3×3 crafting input (1 + x + 3 * y)
10–36	main inventory
37–45	hotbar

Chest

This is the window that is opened when the player right-clicks on a single chest block.

Slot range	Description
0–26	chest
27–53	main inventory
54–62	hotbar

Large chest

This is the window that is opened when the player right-clicks on a double chest block (two adjacent chest blocks).

Slot range	Description
0–53	chest
54–80	main inventory
81–89	hotbar

Furnace

Slot range	Description
0	ingredient
1	fuel
2	output
3–29	main inventory
30–38	hotbar

Dispenser

Slot range	Description
0–8	3×3 dispenser contents (x + 3 * y)
9–35	main inventory
36-44	hotbar

Enchantment Table

Slot range	Description
0	item to enchant
1	lapis lazuli slot
2–28	main inventory
29–37	hotbar