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 15w31a, protocol 49). 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 49)
			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

No changes so far.

Serverbound

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 (currently) be one of six 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 send 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, and all other values 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. The x, y and z fields are all set to 0 like above, with the exception of the face field, which is set to 255.

Status code 6 is another special case. Used to swap or assign an item to the second hand. The rest of the fields (x, y, z and face) are all set to 0.

The face 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

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 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 Nr., 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.

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	Byte	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.

Status

Clientbound

No changes so far.

Serverbound

No changes so far.

Login

Clientbound

No changes so far.

Serverbound

No changes so far.