Pre-release protocol

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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

13w25a: Protocol version is now 71. Changed packet: Increment Statistic (0xC8)

13w24b: Protocol version is now 70

13w24a: Protocol version is now 69. Changed functionality: Time Update (0x04)

13w23b: Protocol version is now 68.

13w22a: Protocol version is now 67. New packet: Entity Properties (0x2C); Changed packets: Chat Message (0x03)

13w18b: Protocol version is now 65.

13w16b: Protocol version is now 63. New packet: Steer Vehicle (0x1B)

13w16a: Protocol version is now 62. Changed packets: Update Health (0x08), Entity Action (0x17), Attach Entity (0x27), Player Abilities (0xCA)

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

Note: The server sends this packet to inform the user of its movement speed. Users move far too fast when this packet is not sent.

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


Server to Client

The chat string must now be a valid JSON object:

   {"text":"§aOld style chat"}

Original Gist from Dinnerbone

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

Time Update (0x04)

Server to Client

Time is based on ticks, where 20 ticks happen every second. There are 24000 ticks in a day, making Minecraft days exactly 20 minutes long.

The time of day is based on the timestamp modulo 24000. 0 is sunrise, 6000 is noon, 12000 is sunset, and 18000 is midnight.

The default SMP server increments the time by 20 every second.

Packet ID Field Name Field Type Example Notes
0x04 Age of the world long 45464654 In ticks; not changed by server commands
Time of Day long 21321 The world (or region) time, in ticks. If negative the sun will stop moving at the Math.abs of the time.
Total Size: 17 Bytes

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

Increment Statistic (0xC8)

Server to Client

Packet ID Field Name Field Type Example Notes
0xC8 Statistic ID int 1003 The ID of the statistic. See List of statistics.
Amount int 1 The amount to increment the statistic.
Total Size: 9 bytes

Player Abilities (0xCA)


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

The client ignores the walking speed and flying speed fields. Send an 0x2C packet as well.

Removed Packets


Changed Data Types


Protocol History