Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.8.8, protocol 47) to the current pre-release (currently 15w31c, protocol 51). Note that this page contains bleeding-edge information that may not be completely or correctly documented.

One who wishes to commandeer the merging of this into Protocol when an update is made must be sure to respect any changes that may have occurred to the respective packets there.

Protocol history

None so far.

New/modified data types

None so far.

Handshaking

Clientbound

No changes so far.

Serverbound

Handshake

This causes the server to switch into the target state.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x00	Handshaking	Server	Protocol Version	VarInt	See protocol version numbers (currently 47 50)
			Server Address	String	hostname or IP, e.g. localhost or 127.0.0.1
			Server Port	Unsigned Short	default is 25565
			Next State	VarInt	1 for status, 2 for login

Play

Clientbound

Entity Equipment

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x04	Play	Client	Entity ID	VarInt	Entity's EID
			Slot	Short Byte	Equipment slot. 0: main hand, 1: off hand, 1–4 2–5: armor slot (2: boots, 3: leggings, 4: chestplate, 5: helmet)
			Item	Slot	Item in slot format

Spawn Object

Sent by the server when an object/vehicle is created.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0E	Play	Client	Entity ID	VarInt	EID of the object
			Object UUID	UUID
			Type	Byte	The type of object (See Entities#Objects)
			X	Int	X position as a Fixed-Point number
			Y	Int	Y position as a Fixed-Point number
			Z	Int	Z position as a Fixed-Point number
			Pitch	Angle
			Yaw	Angle
			Data	Object Data

Spawn Mob

Sent by the server when a mob entity is spawned.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0F	Play	Client	Entity ID	VarInt
			Entity UUID	UUID
			Type	Unsigned Byte	The type of mob. See Entities#Mobs
			X	Int	X position as a Fixed-Point number
			Y	Int	Y position as a Fixed-Point number
			Z	Int	Z position as a Fixed-Point number
			Yaw	Angle
			Pitch	Angle
			Head Pitch	Angle
			Velocity X	Short	Same units as Entity Velocity
			Velocity Y	Short	Same units as Entity Velocity
			Velocity Z	Short	Same units as Entity Velocity
			Metadata	Metadata

Boss Bar

This packet replaces Update Entity NBT packet which has been removed.

Packet ID	State	Bound To	Field Name		Field Type	Notes
0x49	Play	Client	UUID		UUID	Unique ID for this bar
			Action		VarInt
			Action	Field Name
			0: add	Title	Chat
				Health	Float
				Color	VarInt	Color ID (see below)
				Dividers	VarInt
				Flags	Unsigned Byte	Bit mask: 0x1 should darken sky, 0x2: is dragon bar
			1: remove	no fields	no fields	Removes this boss bar
			2: update health	Health	Float
			3: update title	Title	Chat
			4: update style	Color	VarInt
				Dividers	VarInt
			5: update flags	Flags	Unsigned Byte

ID	Color
0	Pink(ish)
1	Cyan
2	Red
3	Lime
4	Yellow
5	Purple
6	White

Serverbound

Use Entity

This packet is sent from the client to the server when the client attacks or right-clicks another entity (a player, minecart, etc).

A Notchian server only accepts this packet if the entity being attacked/used is visible without obstruction and within a 4-unit radius of the player's position.

Note that middle-click in creative mode is interpreted by the client and sent as a Creative Inventory Action packet instead.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x02	Play	Server	Target	VarInt
			Type	VarInt	0: interact, 1: attack, 2: interact at
			Target X	Optional Float	Only if Type is interact at
			Target Y	Optional Float	Only if Type is interact at
			Target Z	Optional Float	Only if Type is interact at
			Hand	Optional Byte	Only if Type is interact or interact at; 0: main hand, 1: off hand

Player Digging

Sent when the player mines a block. A Notchian server only accepts digging packets with coordinates within a 6-unit radius of the player's position.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x07	Play	Server	Status	Byte	The action the player is taking against the block (see below)
			Location	Position	Block position
			Face	Byte	The face being hit (see below)

Status can be one of seven values:

Meaning	Value
Started digging	0
Cancelled digging	1
Finished digging	2
Drop item stack	3
Drop item	4
Shoot arrow / finish eating	5
Swap item in Hand	6

Notchian clients send a 0 (started digging) when they start digging and a 2 (finished digging) once they think they are finished. If digging is aborted, the client simply sends a 1 (cancel digging).

Status code 4 (drop item) is a special case. In-game, when you use the Drop Item command (keypress 'q'), a dig packet with a status of 4, Location set to 0/0/0, and Face set to 0, is sent from client to server. Status code 3 is similar, but drops the entire stack.

Status code 5 (shoot arrow / finish eating) is also a special case. Location is set to 0/0/0 like above, but the face field is set to 255.

Status code 6 is another special case. Used to swap or assign an item to the second hand. Location is set to 0/0/0 and Face is set to 0.

The Face field can be one of six values, representing the face being hit:

Value	0	1	2	3	4	5
Offset	-Y	+Y	-Z	+Z	-X	+X

Use Item

Sent when pressing the Use Item key (default: right click) with an item in hand.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x08	Play	Server	Hand	Byte	Hand used for the animation

Player Block Placement

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x08 0x09	Play	Server	Location	Position	Block position
			Face	Byte	The face on which the block is placed (see above)
			Held Item Hand	Slot Byte	The hand from which the block is placed; 0: main hand, 1: off hand
			Cursor Position X	Byte	The position of the crosshair on the block
			Cursor Position Y	Byte
			Cursor Position Z	Byte

In normal operation (i.e. placing a block), this packet is sent once, with the values set normally.

This packet has a special case where X, Y, Z, and Direction are all -1. (Note that Y is unsigned so set to 255.) This special packet indicates that the currently held item for the player should have its state updated such as eating food, pulling back bows, using buckets, etc.

Special note on using buckets: When using buckets, the Notchian client might send two packets: first a normal and then a special case. The first normal packet is sent when you're looking at a block (e.g. the water you want to scoop up). This normal packet does not appear to do anything with a Notchian server. The second, special case packet appears to perform the action — based on current position/orientation and with a distance check — it appears that buckets can only be used within a radius of 6 units.

Held Item Change

Sent when the player changes the slot selection.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x09 0x0A	Play	Server	Slot	Short	The slot which the player has selected (0–8)

Animation

Sent when the player's arm swings

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0A 0x0B	Play	Server	Hand	Byte	Hand used for the animation

Entity Action

Sent at least when crouching, leaving a bed, or sprinting. To send action animation to client use 0x28. The client will send this with Action ID = 3 when “Leave Bed” is clicked.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0B 0x0C	Play	Server	Entity ID	VarInt	Player ID
			Action ID	VarInt	The ID of the action, see below
			Jump Boost	VarInt	Horse jump boost. Ranged from 0 -> 100.

Action ID can be one of the following values:

ID	Action
0	Crouch
1	Uncrouch
2	Leave bed
3	Start sprinting
4	Stop sprinting
5	Jump with horse
6	Open inventory

Steer Vehicle

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0C 0x0D	Play	Server	Sideways	Float	Positive to the left of the player
			Forward	Float	Positive forward
			Flags	Unsigned Byte	Bit mask. 0x1: jump, 0x2: unmount

Close Window

This packet is sent by the client when closing a window.

Note, Notchian clients send a close window message with Window ID 0 to close their inventory even though there is never an Open Window message for the inventory.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0D 0x0E	Play	Server	Window ID	Unsigned Byte	This is the ID of the window that was closed. 0 for inventory.

Click Window

This packet is sent by the player when it clicks on a slot in a window.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0E 0x0F	Play	Server	Window ID	Unsigned Byte	The ID of the window which was clicked. 0 for player inventory.
			Slot	Short	The clicked slot number, see below
			Button	Byte	The button used in the click, see below
			Action Number	Short	A unique number for the action, implemented by Notchian as a counter, starting at 1. Used by the server to send back a Confirm Transaction.
			Mode	Byte	Inventory operation mode, see below
			Clicked item	Slot	The clicked slot. Has to be empty (item ID = -1) for drop mode.

See Inventory#Windows for further information about how slots are indexed.

When right-clicking on a stack of items, half the stack will be picked up and half left in the slot. If the stack is an odd number, the half left in the slot will be smaller of the amounts.

The distinct type of click performed by the client is determined by the combination of the Mode and Button fields.

Mode	Button	Slot	Trigger
0	0	Normal	Left mouse click
	1	Normal	Right mouse click
1	0	Normal	Shift + left mouse click
	1	Normal	Shift + right mouse click (identical behavior)
2	0	Normal	Number key 1
	1	Normal	Number key 2
	2	Normal	Number key 3
	⋮	⋮	⋮
	8	Normal	Number key 9
3	2	Normal	Middle click
4	0	Normal*	Drop key (Q) (* Clicked item is different, see above)
	1	Normal*	Ctrl + Drop key (Ctrl-Q) (drops full stack)
	0	-999	Left click outside inventory holding nothing (no-op)
	1	-999	Right click outside inventory holding nothing (no-op)
5	0	-999	Starting left mouse drag (or middle mouse)
	4	-999	Starting right mouse drag
	1	Normal	Add slot for left-mouse drag
	5	Normal	Add slot for right-mouse drag
	2	-999	Ending left mouse drag
	6	-999	Ending right mouse drag
6	0	Normal	Double click

Starting from version 1.5, “painting mode” is available for use in inventory windows. It is done by picking up stack of something (more than 1 item), then holding mouse button (left, right or middle) and dragging held stack over empty (or same type in case of right button) slots. In that case client sends the following to server after mouse button release (omitting first pickup packet which is sent as usual):

1. packet with mode 5, slot -999, button (0 for left | 4 for right);
2. packet for every slot painted on, mode is still 5, button (1 | 5);
3. packet with mode 5, slot -999, button (2 | 6);

If any of the painting packets other than the “progress” ones are sent out of order (for example, a start, some slots, then another start; or a left-click in the middle) the painting status will be reset.

The server will send back a Confirm Transaction packet. If the click was not accepted, the client must reflect that packet before sending more Click Window packets, otherwise the server will reject them silently. The Notchian server also sends a Window Items packet for the open window and Set Slot packets for the clicked and cursor slot, but only when the click was not accepted, probably to resynchronize client and server.

Confirm Transaction

<SpaceManiac> noooo idea why the serverbound confirm transaction packet exists
<SpaceManiac> I think it's sent as a response to the clientbound confirm transaction in some situations, but it's fuzzy

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x0F 0x10	Play	Server	Window ID	Byte	The ID of the window that the action occurred in
			Action Number	Short	Every action that is to be accepted has a unique number. This field corresponds to that number.
			Accepted	Boolean	Whether the action was accepted

Creative Inventory Action

While the user is in the standard inventory (i.e., not a crafting bench) in Creative mode, the player will send this packet.

Clicking in the creative inventory menu is quite different from non-creative inventory management. Picking up an item with the mouse actually deletes the item from the server, and placing an item into a slot or dropping it out of the inventory actually tells the server to create the item from scratch. (This can be verified by clicking an item that you don't mind deleting, then severing the connection to the server; the item will be nowhere to be found when you log back in.) As a result of this implementation strategy, the "Destroy Item" slot is just a client-side implementation detail that means "I don't intend to recreate this item.". Additionally, the long listings of items (by category, etc.) are a client-side interface for choosing which item to create. Picking up an item from such listings sends no packets to the server; only when you put it somewhere does it tell the server to create the item in that location.

This action can be described as “set inventory slot”. Picking up an item sets the slot to item ID -1. Placing an item into an inventory slot sets the slot to the specified item. Dropping an item (by clicking outside the window) effectively sets slot -1 to the specified item, which causes the server to spawn the item entity, etc.. All other inventory slots are numbered the same as the non-creative inventory (including slots for the 2×2 crafting menu, even though they aren't visible in the vanilla client).

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x10 0x11	Play	Server	Slot	Short	Inventory slot
			Clicked Item	Slot

Enchant Item

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x11 0x12	Play	Server	Window ID	Byte	The ID of the enchantment table window sent by Open Window
			Enchantment	Byte	The position of the enchantment on the enchantment table window, starting with 0 as the topmost one

Update Sign

This message is sent from the client to the server when the “Done” button is pushed after placing a sign.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x12 0x13	Play	Server	Location	Position	Block Coordinates
			Line 1	Chat	First line of text in the sign
			Line 2	Chat	Second line of text in the sign
			Line 3	Chat	Third line of text in the sign
			Line 4	Chat	Fourth line of text in the sign

Player Abilities

The latter 2 bytes are used to indicate the walking and flying speeds respectively, while the first byte is used to determine the value of 4 booleans.

The vanilla client sends this packet when the player starts/stops flying with the second parameter changed accordingly. All other parameters are ignored by the vanilla server.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x13 0x14	Play	Server	Flags	Byte	Bit mask. 0x08: damage disabled (god mode), 0x04: can fly, 0x02: is flying, 0x01: is Creative
			Flying Speed	Float
			Walking Speed	Float

Tab-Complete

Sent when the user presses tab while writing text.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x14 0x15	Play	Server	Text	String	All text behind the cursor
			Has Position	Boolean
			Looked At Block	Optional Position	The position of the block being looked at. Only sent if Has Position is true

Client Settings

Sent when the player connects, or when settings are changed.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x15 0x16	Play	Server	Locale	String	e.g. en_GB
			View Distance	Byte	Client-side render distance, in chunks
			Chat Mode	Byte	0: enabled, 1: commands only, 2: hidden
			Chat Colors	Boolean	“Colors” multiplayer setting
			Displayed Skin Parts	Unsigned Byte	Skin parts, see note below
			Main Hand	VarInt	0: Left, 1: Right

Displayed Skin Parts flags:

• Bit 0 (0x01): Cape enabled
• Bit 1 (0x02): Jacket enabled
• Bit 2 (0x04): Left Sleeve enabled
• Bit 3 (0x08): Right Sleeve enabled
• Bit 4 (0x10): Left Pants Leg enabled
• Bit 5 (0x20): Right Pants Leg enabled
• Bit 6 (0x40): Hat enabled

The most significant bit (bit 7, 0x80) appears to be unused.

Client Status

Sent when the client is ready to complete login and when the client is ready to respawn after death.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x16 0x17	Play	Server	Action ID	VarInt	See below

Action ID values:

Action ID	Action
0	Perform respawn
1	Request stats
2	Taking Inventory achievement Open Inventory

Plugin Message

Mods and plugins can use this to send their data. Minecraft itself uses a number of plugin channels. These internal channels are prefixed with MC|.

More documentation on this: http://dinnerbone.com/blog/2012/01/13/minecraft-plugin-channels-messaging/

Note that the data length is known from the packet length, so there is no need for a length member being sent.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x17 0x18	Play	Server	Channel	String	Name of the plugin channel used to send the data
			Data	Byte Array	Any data, depending on the channel. MC| channels are documented here.

Spectate

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x18 0x19	Play	Server	Target Player	UUID

Resource Pack Status

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x19 0x1A	Play	Server	Hash	String	The hash sent in the Resource Pack Send packet.
			Result	VarInt	0: successfully loaded, 1: declined, 2: failed download, 3: accepted

Status

Clientbound

No changes so far.

Serverbound

No changes so far.

Login

Clientbound

No changes so far.

Serverbound

No changes so far.