Revision as of 17:49, 11 September 2015 by Gjum (talk | contribs) (server sends uniqueSlots = 0 for non-storage windows)
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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.

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 9 unique slots (10 in the 1.9 snapshots).

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 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:

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


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


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


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