Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.6.2, protocol 74) to the current pre-release. 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 History

13w36a - Added sound category byte to 0x3E - Changed 0xC8 to a string:int map

13w37b -

1.6.3 - Terrain fixes to help moving to 1.7, no packet changes from 1.6.2

1.6.4 -

13w38a/b/c -

13w39a/b - UUIDs added to spawn named entity, game state 'gamemode' byte -> float

13w41a - Large protocol work

Protocol Version

13w41a -

13w39a/b - 80

13w38a/b/c - 79

1.6.4 - 78

1.6.3 - 77

13w37b - 76

13w36a - 75

Packet format

Field Name	Field Type	Notes
Length	VarInt
Type	VarInt
Data

Data Types

VarInt -

String - UTF-8 String

Handshaking

Serverbound

Packet ID	Field Name	Field Type	Notes
0x00		VarInt
		String
		VarInt
		VarInt

Play

Clientbound

Keep Alive

Packet ID	Field Name	Field Type	Notes
0x00	Keep Alive ID	Int

Join Game

Packet ID	Field Name	Field Type	Notes
0x01	Entity ID	Int	The player's Entity ID
	Level type	String	level-type in server.properties
	Gamemode	Byte	0: survival, 1: creative, 2: adventure. Bit 3 (0x8) is the hardcore flag
	Dimension	Byte	-1: nether, 0: overworld, 1: end
	Difficulty	Unsigned Byte	0 thru 3 for Peaceful, Easy, Normal, Hard
		Byte
	Max Players	Byte	Used by the client to draw the player list

Chat Message

Packet ID	Field Name	Field Type	Notes
0x02	JSON Data	String	https://gist.github.com/thinkofdeath/e882ce057ed83bac0a1c

Time Update

Packet ID	Field Name	Field Type	Notes
0x03	Age of the world	Long	In ticks; not changed by server commands
	Time of day	Long	The world (or region) time, in ticks. If negative the sun will stop moving at the Math.abs of the time

Plugin Channels

MC|RPack

Field Name	Field Type	Example	Notes
Resource pack URL	UTF8 string	http://example.com/pack.zip