Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.5.2, protocol 61) to the current pre-release, 13w17a (protocol 64). Note that this page contains bleeding-edge information that may not be completely or correctly documented.

He 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 occured to the respective packets there.

Protocol Version

As of 13w22a the protocol version is 67.

New Packets

Steer Vehicle (0x1B)

Client to Server

Sent by client to steer the horse, minecart and boats. Horses listen to all directions, boats and minecarts only listen to the positive forward value in combination with the direction the player is looking in.

Packet ID	Field Name	Field Type	Example	Notes
0x1B	Sideways	float	0.98	Positive to the left of the player
	Forward	float	-0.98	Positive forward
	Jump	bool	true
	Unmount	bool	false	True when leaving the vehicle
Total Size:	11 bytes

Entity Properties (0x2C)

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x2C	EntityID	int	195	?
	Properties Count	int	3	Number of string/data pairs that follow. The remaining fields here are repeated this number of times.
	Key	string16	"generic.Maxhealth"
	Value	double	20.0
	Total Size:	? bytes

Known values:

Key	Default	Min	Max	Label
generic.maxHealth	20.0	0.0	Double.MaxValue	Max Health
generic.followRange	32.0	0.0	2048.0	Follow Range
generic.knockbackResistance	0.0	0.0	1.0	Knockback Resistance
generic.movementSpeed	0.699999988079071	0.0	Double.MaxValue	Movement Speed
generic.attackDamage	2.0	0.0	Double.MaxValue
horse.jumpStrength	0.7	0.0	2.0	Jump Strength
zombie.spawnReinforcements	0.0	0.0	1.0	Spawn Reinforcements Chance

Changed Packets

Chat Message (0x03)

Client to Server

Unchanged

Server to Client

The chat string must now be a valid JSON object:

   {"translate":"chat.type.announcement","using":["Server","hi"]}
   {"color":"gray","italic":true,"translate":"chat.type.admin","using":["Server",{"translate":"commands.save.success"}]}
   {"text":"§aOld style chat"}

Where translate is one of the following:

   chat.type.admin: [%s: %s]
   chat.type.announcement: [%s] %s
   chat.type.emote: * %s %s
   chat.type.text: <%s> %s

Update Health (0x08)

Server to Client

Sent by the server to update/set the health of the player it is sent to. Added in protocol version 5.

Food saturation acts as a food "overcharge". Food values will not decrease while the saturation is over zero. Players logging in automatically get a saturation of 5.0. Eating food increases the saturation as well as the food bar.

Packet ID	Field Name	Field Type	Example	Notes
0x08	Health	float	20.0	0 or less = dead, 20 = full HP
	Food	short	20	0 - 20
	Food Saturation	float	5.0	Seems to vary from 0.0 to 5.0 in integer increments
Total Size:	11 bytes

Entity Action (0x13)

Client to Server

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	Field Name	Field Type	Example	Notes
0x13	EID	int	55534	Player ID
	Action ID	byte	1	The ID of the action, see below.
	Unknown	int	0	Something to do with horses. Ranged from 0 -> 90
Total Size:	10 bytes

Action ID can be one of the following values:

ID	Action
1	Crouch
2	Uncrouch
3	Leave bed
4	Start sprinting
5	Stop sprinting

Attach Entity (0x27)

Server to Client

This packet is sent when a player has been attached to an entity (e.g. Minecart)

Packet ID	Field Name	Field Type	Example	Notes
0x27	Entity ID	int	1298	The player entity ID being attached
	Vehicle ID	int	1805	The vehicle entity ID attached to (-1 for unattaching)
	Leash	boolean	false	If set to true, leashes the entity to the vehicle
Total Size:	10 bytes

Player Abilities (0xCA)

Two-Way

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 flags are whether damage is disabled (god mode, 8, bit 3), whether the player can fly (4, bit 2), whether the player is flying (2, bit 1), and whether the player is in creative mode (1, bit 0).

To get the values of these booleans, simply AND (&) the byte with 1,2,4 and 8 respectively, to get the 0 or 1 bitwise value. To set them OR (|) them with their repspective masks. 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	Field Name	Field Type	Example	Notes
0xCA	Flags	byte	5
	Flying speed	float	0.05	previous integer value divided by 250
	Walking speed	float	0.1	previous integer value divided by 250
Total Size:	10 bytes

Removed Packets

-None-

Changed Data Types

-None-

Protocol History

-None-