Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.9.4, protocol 110) to the current pre-release (currently 16w21b, protocol 203). 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.

Contents

Data types

No changes so far.

Packets

ID	Packet name	Documentation
Handshaking serverbound
0x00	Handshake	Current	Pre
Play clientbound
0x19	Named Sound Effect	Current	Pre
0x46	Sound Effect	Current	Pre

New/modified data types

Mobs

Mobs are spawned via Spawn Mob. There are two extra mob types in the code that refer to mobs classes that can never spawn: Mob and Monster (they are always subclasses, aka another more specific type).

Type	Name	x, z	y
48	Mob	N/A	N/A
49	Monster	N/A	N/A
50	Creeper	0.6	1.8
51	Skeleton	0.6	1.95
52	Spider	1.4	0.9
53	Giant Zombie	0.6 * 6	1.8 * 6
54	Zombie	0.6	1.8
55	Slime	0.51000005 * size	0.51000005 * size
56	Ghast	4	4
57	Zombie Pigman	0.6	1.8
58	Enderman	0.6	2.9
59	Cave Spider	0.7	0.5
60	Silverfish	0.4	0.3
61	Blaze	0.6	1.8
62	Magma Cube	0.51000005 * size	0.51000005 * size
63	Ender Dragon	16.0	8.0
64	Wither	0.9	3.5
65	Bat	0.5	0.9
66	Witch	0.6	1.8
67	Endermite	0.4	0.3
68	Guardian	0.85	0.85
69	Shulker	1	1
90	Pig	0.9	0.9
91	Sheep	0.9	1.3
92	Cow	0.9	1.3
93	Chicken	0.4	0.7
94	Squid	0.95	0.95
95	Wolf	0.6	0.8
96	Mooshroom	0.9	1.3
97	Snowman	0.7	1.9
98	Ocelot	0.6	0.8
99	Iron Golem	1.4	2.9
100	Horse	1.4	1.6
101	Rabbit	0.6	0.7
102	Polar Bear	1.3	1.4
120	Villager	0.6	1.8

Entity Metadata

Note that entity metadata is a totally distinct concept from block metadata. All entities must send at least one item of metadata, in most cases this will be the health item.

An Entity Metadata is an array of entries, each of which looks like the following:

Name	Type	Meaning
Index	Unsigned Byte	Unique index key determining the meaning of the following value, see the table below. If this is 0xff then the it is the end of the Entity Metadata array and no more is read.
Type	Optional Byte Enum	Only if Index is not 0xff; the type of the index, see the table below
Value	Optional value of Type	Only if Index is not 0xff: the value of the metadata field

Value of Type field	Type of Value field	Notes
0	Byte
1	VarInt
2	Float
3	String
4	Chat
5	Slot
6	Boolean
7	Rotation	3 floats: rotation on x, rotation on y, rotation on z
8	Position
9	OptPosition (Boolean + Optional Position)	Position is present if the Boolean is set to true
10	Direction (VarInt)	(Down = 0, Up = 1, North = 2, South = 3, West = 4, East = 5)
11	OptUUID (Boolean + Optional UUID)	UUID is present if the Boolean is set to true
12	BlockID (VarInt)	id << 4 | data

Entity classes also recursively use fields from classes they extend.

Entity class	Index	Type	Meaning
Entity	0	Byte	Bit Mask	Meaning
			0x01	On Fire
			0x02	Crouched
			0x08	Sprinting
			0x10	Eating/Drinking/Blocking
			0x20	Invisible
			0x40	Glowing Effect
			0x80	Flying with Elytra
	1	VarInt	Air
	2	String	Custom Name
	3	Boolean	Is Custom Name Visible
	4	Boolean	Is Silent
	5	Boolean	No Gravity
	6	Boolean	FallFlying
Potion extends Entity	5 7	Slot	Potion which is thrown
FallingBlock extends Entity	5 7	Position	Spawn Position
AreaEffectCloud extends Entity	5 7	Float	Radius
	6 8	VarInt	Color (only for mob spell particle)
	7 9	Boolean	Ignore radius and show effect as single point, not area
	8 10	VarInt	Particle ID
Arrow extends Entity	5 7	Byte	Is Critical
TippedArrow extends Arrow	6 8	VarInt	Color
Boat extends Entity	5 7	VarInt	Time Since Last Hit
	6 8	VarInt	Forward Direction
	7 9	Float	Damage Taken
	8 10	VarInt	Type
	9 11	Boolean	Right paddle turning
	10 12	Boolean	Left paddle turning
EnderCrystal extends Entity	5 7	OptPosition	Beam Target
	6 8	Boolean	Show Bottom
Fireball extends Entity	no additional metadata
WitherSkull extends Fireball	5 7	Boolean	Invulnerable
Fireworks extends Entity	5 7	Slot	Firework Info
Hanging extends Entity	no additional metadata
ItemFrame extends Hanging	5 7	Slot	Item
	6 8	VarInt	Rotation
Item extends Entity	5 7	Slot	Item
Living extends Entity	5 6	Byte	Likely used to limit placing blocks from both hands at the same time.
	6 8	Float	Health
	7 9	VarInt	Potion Effect Color
	8 10	Boolean	Is Potion Effect Ambient
	9 11	VarInt	Number of Arrows in Entity
ArmorStand extends Living
	10 12	Byte	Status bit mask
	11 13	Vector3F	Head rotation
	12 14	Vector3F	Body rotation
	13 15	Vector3F	Left arm rotation
	14 16	Vector3F	Right arm rotation
	15 17	Vector3F	Left leg rotation
	16 18	Vector3F	Right leg rotation
Insentient extends Living	10 12	Byte	Status bit mask (NoAI, Left handed)
Ambient extends Insentient	no additional metadata
Bat extends Ambient	11 13	Byte	Is Hanging
Creature extends Insentient	no additional metadata
Ageable extends Creature	11 13	Boolean	Is Baby
PolarBear extends Ageable	13	Boolean	Is Standing
Animal extends Ageable	no additional metadata
Horse extends Animal	12 14	Byte	Status bit mask
	13 15	VarInt	Type
	14 16	VarInt	Variant
	15 17	OptUUID	Owner's UUID
	16 18	VarInt	Armor
Pig extends Animal	12 14	Boolean	Has Saddle
Rabbit extends Animal	12 14	VarInt	Type
Sheep extends Animal	12 14	Byte	Status bit mask
TameableAnimal extends Animal	12 14	Byte	Status bit mask (sitting, tamed)
	13 15	OptUUID	Owner's UUID
Ocelot extends TameableAnimal	14 16	VarInt	Type
Wolf extends TameableAnimal	14 16	Float	Damage Taken (used for tail rotation)
	15 17	Boolean	Is Begging
	16 18	VarInt	Collar Color
Villager extends Ageable	12 14	VarInt	Profession (Farmer = 0, Librarian = 1, Priest = 2, Blacksmith = 3, Butcher = 4)
Golem extends Creature	no additional metadata
IronGolem extends Golem	11 13	Byte	Is Player Created
Shulker extends Golem	11 13	Direction	Facing Direction
	12 14	OptPosition	Attachment Position
	13 15	Byte	Shield Height
Monster extends Creature	no additional metadata
Blaze extends Monster	11 13	Byte	Is On Fire
Creeper extends Monster	11 13	VarInt	State (-1 = Idle, 1 = Fuse)
	12 14	Boolean	Is Powered
	13 15	Boolean	Is Ignited
Guardian extends Monster	11 13	Byte	Status bit mask (elderly, retracting spikes)
	12 14	VarInt	Target EID
Skeleton extends Monster	11 13	VarInt	Type (0 = Default, 1 = Wither, 2 = Stray)
	12 14	Boolean	Is swinging arms
Spider extends Monster	11 13	Byte	Is Climbing
Witch extends Monster	11 13	Boolean	Is Aggresive
Wither extends Monster	11 13	VarInt	First Head's Target
	12 14	VarInt	Second Head's Target
	13 15	VarInt	Third Head's Target
	14 16	VarInt	Invulnerable Time
Zombie extends Monster	11 13	Boolean	Is Baby
	12 14	VarInt	Is Villager (Profession) Zombie Type (0 = Default, 1-5 = Villager Profession, 6 = Husk)
	13 15	Boolean	Is Converting
	14 16	Boolean	Are Hands Rised Up
Enderman extends Monster	11 13	Block ID	Carried Block
	12 14	Boolean	Is Screaming
EnderDragon extends Insentient	11 13	VarInt	Dragon Phase
Flying extends Insentient	no additional metadata
Ghast extends Flying	11 13	Boolean	Is Attacking
Slime extends Insentient	11 13	VarInt	Size
Minecart extends Entity	5 7	VarInt	Shaking Power
	6 8	VarInt	Shaking Direction
	7 9	Float	Shaking Multiplier
	8 10	VarInt	Block ID and Meta
	9 10	VarInt	Block Y Position
	10 12	Boolean	Show Block
MinecartCommandBlock extends Minecart	11 13	String	Command
	12 14	Chat	Last Output
MinecartFurnace extends Minecart	11 13	Boolean	Is Powered
TNTPrimed extends Entity	5 7	VarInt	Fuse Time

MC|Struct plugin channel

Client to server

Sets information about the inaccessible new Structure block.

Field Name	Field Type	Notes
X	Int	Tile entity location
Y	Int	Tile entity location
Z	Int	Tile entity location
Action	Byte	See below
Mode	String enum	One of "SAVE", "LOAD", "CORNER", "DATA".
Name	String
Offset X	Int	Between -32 and 32
Offset Y	Int	Between -32 and 32
Offset Z	Int	Between -32 and 32
Size X	Int	Between 0 and 32
Size Y	Int	Between 0 and 32
Size Z	Int	Between 0 and 32
Mirror	String enum	One of "NONE", "LEFT_RIGHT", "FRONT_BACK".
Rotation	String enum	One of "NONE", "CLOCKWISE_90", "CLOCKWISE_180", "COUNTERCLOCKWISE_90".
Metadata	String
Ignore entities	Boolean
Show air	Boolean
Show bounding box	Boolean
Integrity	Float	Between 0 and 1
Seed	VarLong

Possible modes:

• 2 - Save the structure
• 3 - Load the structure
• 4 - Detect size

Handshaking

Clientbound

No changes so far.

Serverbound

No changes so far.

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 110 203)
			Server Address	String	Hostname or IP, e.g. localhost or 127.0.0.1, that was used to connect. The Notchian server does not use this information.
			Server Port	Unsigned Short	Default is 25565. The Notchian server does not use this information.
			Next State	VarInt Enum	1 for status, 2 for login

Play

Clientbound

Named Sound Effect

See also: #Sound Effect

Used to play a sound effect on the client. Custom sounds may be added by resource packs.

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x19	Play	Client	Sound Name	String	All known sound effect names can be seen here.
			Sound Category	VarInt Enum	The category that this sound will be played from (current categories)
			Effect Position X	Int	Effect X multiplied by 8 (fixed-point number with only 3 bits dedicated to the fractional part)
			Effect Position Y	Int	Effect Y multiplied by 8 (fixed-point number with only 3 bits dedicated to the fractional part)
			Effect Position Z	Int	Effect Z multiplied by 8 (fixed-point number with only 3 bits dedicated to the fractional part)
			Volume	Float	1 is 100%, can be more
			Pitch	Unsigned Byte Float	63 is 100%, can be more

Sound Effect

This packet is used to play a number of hardcoded sound events. For custom sounds, use Named Sound Effect (Play, 0x19, clientbound).

Numeric sound effect IDs are liable to change between versions

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x46	Play	Client	Sound ID	VarInt	ID of hardcoded sound event (events)
			Sound Category	VarInt Enum	The category that this sound will be played from (current categories)
			Effect Position X	Int	Effect X multiplied by 8 (fixed-point number with only 3 bits dedicated to the fractional part)
			Effect Position Y	Int	Effect Y multiplied by 8 (fixed-point number with only 3 bits dedicated to the fractional part)
			Effect Position Z	Int	Effect Z multiplied by 8 (fixed-point number with only 3 bits dedicated to the fractional part)
			Volume	Float	1.0 is 100%, capped between 0.0 and 1.0 by Notchian clients
			Pitch	Unsigned Byte Float	Float multiplied by 63.5, capped between 0.5 and 2.0 by Notchian clients

Serverbound

No changes so far.

Status

Clientbound

No changes so far.

Serverbound

No changes so far.

Login

Clientbound

No changes so far.

Serverbound

No changes so far.