Entity metadata

Entity Metadata Format

Note that entity metadata is a totally distinct concept from block metadata.

The entity metadata format is quirky dictionary format, where the key and the value's type are packed in a single byte.

To parse, repeat the following procedure:

1) Read an unsigned byte
2) If this byte == 127, stop reading
3) Decompose the byte. 
   The bottom 5 bits (0x1F) serve as an identifier (key) for the data to follow. 
   The top 3 bits (0xE0) serve as a type:
    0: byte
    1: short
    2: int
    3: float
    4: string16,
    5: short, byte, short (slot type)
    6: int, int, int
4) Read and unpack based on the type (above)

In python:

   #socket is positioned at the beginning of the metadata array
   metadata = {}
   x = socket.unpack('byte')
   while x != 127:
       index = x & 0x1F # Lower 5 bits
       ty    = x >> 5   # Upper 3 bits
       if ty == 0: val = socket.unpack('byte') 
       if ty == 1: val = socket.unpack('short') 
       if ty == 2: val = socket.unpack('int') 
       if ty == 3: val = socket.unpack('float') 
       if ty == 4: val = socket.unpack('string16')
       if ty == 5:
           val = {}
           val["id"]     = socket.unpack('short')
           val["count"]  = socket.unpack('byte')
           val["damage"] = socket.unpack('short')
       if ty == 6:
           val = []
           for i in range(3):
               val.append(socket.unpack('int'))
       metadata[index] = (ty, val)
       x = socket.unpack('byte')
   return metadata

Common Metadata

Index 0, byte: Flags

All mobs, objects and players send metadata with index 0. The value is a byte representing 8 boolean flags:

Bit index	Bit mask	Meaning
0	0x01	Entity on fire
1	0x02	Entity crouched
2	0x04	Entity riding
3	0x08	Sprinting
4	0x10	Eating/Drinking

Index 1, short: Unknown

Seems to be sent for *at least* all mobs. I've only seen 300 as a value so far.

Index 8, int: Potion effects

Players and most (all?) mobs send metadata with index 8. This specifies the colour of the bubbling effects around the player.

The value is an int, that should be decomposed into four 4-bit nibbles, representing 0x00RRGGBB

If the value is 0, no potion effects currently apply to the entity.

Index 12, int: Animals

0 for ordinary animals.

Baby animals have the value -23999. This corresponds to the number of ticks in a minecraft day, which is how long it takes for a baby animal to "grow up". It is therefore considered likely that this field determines the size of the animal, and that Entity Metadata will update it as the animal grows. This needs to be confirmed by someone!

Mobs

Mobs are spawned via 0x18 Mob Spawn

Type	Name	x, z	y
50	Creeper	0.6	1.8
51	Skeleton	0.6	1.8
52	Spider	1.4	0.9
53	Giant Zombie	3.6	10.8
54	Zombie	0.6	1.8
55	Slime	0.6 * size	0.6 * size
56	Ghast	4	4
57	Zombie Pigman	0.6	1.8
58	Enderman
59	Cave Spider
60	Silverfish
61	Blaze
62	Magma Cube	0.6 * size	0.6 * size
63	Ender Dragon
90	Pig	0.9	0.9
91	Sheep	0.6	1.3
92	Cow	0.9	1.3
93	Duck	0.3	0.4
94	Squid	0.95	0.95
95	Wolf	0.6	1.8
96	Mooshroom
97	Snowman
120	Villager

Extra Metadata

Creeper

• Index 16 (byte): Status. Depends on the fuse
• Index 17 (byte): Charged. 1 if the creeper has been hit by lightning, 0 otherwise.

Spider

• Index 16 (byte): Unknown - possibly aggression.

Slime / Magma Cube

• Index 16 (byte): Size. Randomly-generated. 0, 1, 2 or 4.

Ghast

• Index 16 (byte): Aggression. 1 for aggressive (red eyes), 0 otherwise.

Enderman

• Index 16 (byte): Item in hand
• Index 17 (byte): Aggression. 1 for aggressive, 0 otherwise.

Blaze

• Index 16 (byte): Attacking. 1 sets the blaze on fire, and shortly after it will attack. 0 signals the end of the attack.

Pig

• Index 16 (byte): Saddled. 1 if the pig is wearing a saddle, 0 otherwise.

Sheep

• Index 16 (byte): bit 0x10 indicates shearedness. bits 0x0F indicate color (see below).

Index	Wool Color
0	White
1	Orange
2	Magenta
3	Light Blue
4	Yellow
5	Lime
6	Pink
7	Gray
8	Silver
9	Cyan
10	Purple
11	Blue
12	Brown
13	Green
14	Red
15	Black

Wolf

• Index 16 (byte): Flags (see below).
• Index 17 (string): Name of player that tamed wolf.
• Index 18 (int): Health.

Bit index	Bit mask	Meaning
0	0x01	Sitting down
1	0x02	Aggressive (red eyes)
2	0x04	Tamed

Objects

Objects are spawned via 0x17 Add Object/Vehicle

ID	Name	x, z	y
1	Boat	1.5	0.6
10	Minecart	0.98	0.7
11	Minecart (storage)	0.98	0.7
12	Minecart (powered)	0.98	0.7
50	Activated TNT	0.98	0.98
51	EnderCrystal	1.25?	2.25?
60	Arrow (projectile)	0.5	0.5
61	Snowball (projectile)	0.25	0.25
62	Egg (projectile)	0.25	0.25
70	Falling Sand	0.98	0.98
71	Falling Gravel	0.98	0.98
90	Fishing Float	0.25?	0.25?

Other

Players are spawned via 0x14 Named Entity Spawn. They have dimensions 0.6 * 1.8.

Pickups are spawned via 0x15 Pickup Spawn. They have dimensions 0.25 * 0.25.