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 Window packet indicates which window is being opened according to:

Window Type	Description
minecraft:container	Fallback for unknown types; also used for Ender chests. Behaves the same as minecraft:chest.
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.

For all windows, the slot in the upper-left corner of the player's inventory is slot n where n is the number of unique slots, and slot number -999 is always used for clicking outside the window.

The number of unique slots in the window is sent in the Open Window (Play, 0x2d, clientbound) packet for all storage windows (e.g. Chest, Dropper). For non-storage windows (the items get dropped when the window is closed, e.g. Workbench, Anvil), the received number of unique slots is always 0, but it can be looked up by the client from the window type.

The default inventory window, which is never explicitly opened by the server, has 10 unique slots.

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.

Using -1 as slot index and as window id will set the cursor item (the stack dragged with the mouse).

Player 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
45	Offhand slot

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

Chest

Chest slots

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

Double/large chest slots

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

It is possible to receive different "Number Of Slots" parameters than those two. In vanilla, using /setblock four times around a chest and then opening the middle chest will open a window with 5*27 chest slots. Some custom servers will send chest inventories with other sizes, usually ranging from 1 row to 6 rows. These may be used for custom GUIs. It is thus important to correctly use the "Number Of Slots" parameter in the open window packet to determine the number of rows in the chest, rather than hardcoding what constitutes a regular chest or a large chest.

Crafting table

Crafting table slots

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

Furnace

Furnace slots

The window that appears when a furnace is right-clicked.

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

Dispenser

Dispenser/dropper slots

The inventory that appears when a dispenser or dropper is opened.

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

Enchantment Table

Enchantment table slots

The inventory of an enchantment table. The enchant buttons trigger a Enchant item packet.

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

Brewing stand

Brewing stand slots

The GUI that appears when a brewing stand is opened.

Slot range	Description
0-2	bottles/potions
3	potion ingredient
4	blaze powder
5-31	main inventory
32-40	hotbar

Villager trading

Villeger slots

The GUI that appears when a villager is right-clicked. Note that if the villager only requires one item, you can put it in either (or both) slots.

Slot range	Description
0-1	input items
2	result
3–29	main inventory
30–38	hotbar

Beacon

Beacon slots

The window that appears when a beacon is right-clicked.

Slot range	Description
0	payment item
1–27	main inventory
28–36	hotbar

Anvil

Anvil slots

Slot range	Description
0	first item
1	second item
2	result
3–29	main inventory
30–38	hotbar

Hopper

Hopper slots

The window that appears when a hopper or hopper minecart is opened.

Slot range	Description
0-4	hopper slots
5–31	main inventory
32–40	hotbar

Horse

Horse slots

The window for when a tamed horse is right-clicked or the player's inventory is opened while riding a horse.

Slot range	Description
0	saddle
1	armor
2–28	main inventory
29–37	hotbar

• 

  Horse slots

• 

  Skeleton horse slots

• 

  Zombie horse slots

Donkey

Donkey slots

The inventory that appears when a tamed donkey (or mule?) is right-clicked, or when the player's inventory is opened while riding a tamed donkey or mule.

There still is an armor slot, even though it cannot be used and is invisible.

Slot range	Description
0	saddle
1	armor
2–16	donkey inventory
17–43 (2-28 if unchested)	player inventory
44–52 (29-37 if unchested)	hotbar

• 

  Unchested donkey

• 

  Chested donkey

• 

  Unchested mule

• 

  Chested mule