Data types

This article defines the data types used in the protocol. All data sent over the network (except for VarInt and VarLong) is big-endian, that is the bytes are sent from most significant byte to least significant byte. The majority of everyday computers are little-endian, therefore it may be necessary to change the endianness before sending data over the network.

Definitions

Name	Size (bytes)	Encodes	Notes
Boolean	1	Either false or true	True is encoded as 0x01, false as 0x00.
Byte	1	An integer between -128 and 127	Signed 8-bit integer, two's complement
Unsigned Byte	1	An integer between 0 and 255	Unsigned 8-bit integer
Short	2	An integer between -32768 and 32767	Signed 16-bit integer, two's complement
Unsigned Short	2	An integer between 0 and 65535	Unsigned 16-bit integer
Int	4	An integer between -2147483648 and 2147483647	Signed 32-bit integer, two's complement
Long	8	An integer between -9223372036854775808 and 9223372036854775807	Signed 64-bit integer, two's complement
Float	4	A single-precision 32-bit IEEE 754 floating point number
Double	8	A double-precision 64-bit IEEE 754 floating point number
String (n)	≥ 1 ≤ (n×3) + 3	A sequence of Unicode scalar values	Modified UTF-8 string prefixed with its size in bytes as a VarInt. Maximum length of n characters, which varies by context; up to n × 3 bytes can be used to encode n characters and both of those limits are checked. Maximum n value is 32767. The + 3 is due to the max size of a valid length VarInt.
Chat	Varies	See Chat	Encoded as a NBT Tag, with the type of tag used depending on the case: As a String Tag: For components only containing text (no styling, no events etc.). As a Compound Tag: Every other case.
Json Chat	≥ 1 ≤ (262144×3) + 3	See Chat	Encoded as a String with max length of 262144.
Identifier	≥ 1 ≤ (32767×3) + 3	See Identifier below	Encoded as a String with max length of 32767.
VarInt	≥ 1 ≤ 5	An integer between -2147483648 and 2147483647	Variable-length data encoding a two's complement signed 32-bit integer; more info in their section
VarLong	≥ 1 ≤ 10	An integer between -9223372036854775808 and 9223372036854775807	Variable-length data encoding a two's complement signed 64-bit integer; more info in their section
Entity Metadata	Varies	Miscellaneous information about an entity	See Entity_metadata#Entity Metadata Format
Slot	Varies	An item stack in an inventory or container	See Slot Data
NBT Tag	Varies	Depends on context	See NBT
Position	8	An integer/block position: x (-33554432 to 33554431), z (-33554432 to 33554431), y (-2048 to 2047)	x as a 26-bit integer, followed by z as a 26-bit integer, followed by y as a 12-bit integer (all signed, two's complement). See also the section below.
Angle	1	A rotation angle in steps of 1/256 of a full turn	Whether or not this is signed does not matter, since the resulting angles are the same.
UUID	16	A UUID	Encoded as an unsigned 128-bit integer (or two unsigned 64-bit integers: the most significant 64 bits and then the least significant 64 bits)
Optional X	0 or size of X	A field of type X, or nothing	Whether or not the field is present must be known from the context.
Array of X	count times size of X	Zero or more fields of type X	The count must be known from the context.
X Enum	size of X	A specific value from a given list	The list of possible values and how each is encoded as an X must be known from the context. An invalid value sent by either side will usually result in the client being disconnected with an error or even crashing.
Byte Array	Varies	Depends on context	This is just a sequence of zero or more bytes, its meaning should be explained somewhere else, e.g. in the packet description. The length must also be known from the context.

Identifier

Identifiers are a namespaced location, in the form of minecraft:thing. If the namespace is not provided, it defaults to minecraft (i.e. thing is minecraft:thing). Custom content should always be in its own namespace, not the default one. Both the namespace and value can use all lowercase alphanumeric characters (a-z and 0-9), dot (.), dash (-), and underscore (_). In addition, values can use slash (/). The naming convention is lower_case_with_underscores. More information. For ease of determining whether a namespace or value is valid, here are regular expressions for each:

• Namespace: [a-z0-9.-_]
• Value: [a-z0-9.-_/]

VarInt and VarLong

Variable-length format such that smaller numbers use fewer bytes. These are very similar to Protocol Buffer Varints: the 7 least significant bits are used to encode the value and the most significant bit indicates whether there's another byte after it for the next part of the number. The least significant group is written first, followed by each of the more significant groups; thus, VarInts are effectively little endian (however, groups are 7 bits, not 8).

VarInts are never longer than 5 bytes, and VarLongs are never longer than 10 bytes. Within these limits, unnecessarily long encodings (e.g. 81 00 to encode 1) are allowed.

Pseudocode to read and write VarInts and VarLongs:

private static final int SEGMENT_BITS = 0x7F;
private static final int CONTINUE_BIT = 0x80;

public int readVarInt() {
    int value = 0;
    int position = 0;
    byte currentByte;

    while (true) {
        currentByte = readByte();
        value |= (currentByte & SEGMENT_BITS) << position;

        if ((currentByte & CONTINUE_BIT) == 0) break;

        position += 7;

        if (position >= 32) throw new RuntimeException("VarInt is too big");
    }

    return value;
}

public long readVarLong() {
    long value = 0;
    int position = 0;
    byte currentByte;

    while (true) {
        currentByte = readByte();
        value |= (long) (currentByte & SEGMENT_BITS) << position;

        if ((currentByte & CONTINUE_BIT) == 0) break;

        position += 7;

        if (position >= 64) throw new RuntimeException("VarLong is too big");
    }

    return value;
}

public void writeVarInt(int value) {
    while (true) {
        if ((value & ~SEGMENT_BITS) == 0) {
            writeByte(value);
            return;
        }

        writeByte((value & SEGMENT_BITS) | CONTINUE_BIT);

        // Note: >>> means that the sign bit is shifted with the rest of the number rather than being left alone
        value >>>= 7;
    }
}

public void writeVarLong(long value) {
    while (true) {
        if ((value & ~((long) SEGMENT_BITS)) == 0) {
            writeByte(value);
            return;
        }

        writeByte((value & SEGMENT_BITS) | CONTINUE_BIT);

        // Note: >>> means that the sign bit is shifted with the rest of the number rather than being left alone
        value >>>= 7;
    }
}

Note Minecraft's VarInts are identical to LEB128 with the slight change of throwing a exception if it goes over a set amount of bytes.

Note that Minecraft's VarInts are not encoded using Protocol Buffers; it's just similar. If you try to use Protocol Buffers Varints with Minecraft's VarInts, you'll get incorrect results in some cases. The major differences:

• Minecraft's VarInts are all signed, but do not use the ZigZag encoding. Protocol buffers have 3 types of Varints: uint32 (normal encoding, unsigned), sint32 (ZigZag encoding, signed), and int32 (normal encoding, signed). Minecraft's are the int32 variety. Because Minecraft uses the normal encoding instead of ZigZag encoding, negative values always use the maximum number of bytes.
• Minecraft's VarInts are never longer than 5 bytes and its VarLongs will never be longer than 10 bytes, while Protocol Buffer Varints will always use 10 bytes when encoding negative numbers, even if it's an int32.

Sample VarInts:

Value	Hex bytes	Decimal bytes
0	0x00	0
1	0x01	1
2	0x02	2
127	0x7f	127
128	0x80 0x01	128 1
255	0xff 0x01	255 1
25565	0xdd 0xc7 0x01	221 199 1
2097151	0xff 0xff 0x7f	255 255 127
2147483647	0xff 0xff 0xff 0xff 0x07	255 255 255 255 7
-1	0xff 0xff 0xff 0xff 0x0f	255 255 255 255 15
-2147483648	0x80 0x80 0x80 0x80 0x08	128 128 128 128 8

Sample VarLongs:

Value	Hex bytes	Decimal bytes
0	0x00	0
1	0x01	1
2	0x02	2
127	0x7f	127
128	0x80 0x01	128 1
255	0xff 0x01	255 1
2147483647	0xff 0xff 0xff 0xff 0x07	255 255 255 255 7
9223372036854775807	0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0x7f	255 255 255 255 255 255 255 255 127
-1	0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0x01	255 255 255 255 255 255 255 255 255 1
-2147483648	0x80 0x80 0x80 0x80 0xf8 0xff 0xff 0xff 0xff 0x01	128 128 128 128 248 255 255 255 255 1
-9223372036854775808	0x80 0x80 0x80 0x80 0x80 0x80 0x80 0x80 0x80 0x01	128 128 128 128 128 128 128 128 128 1

Position

Note: What you are seeing here is the latest version of the Data types article, but the position type was different before 1.14.

64-bit value split into three signed integer parts:

• x: 26 MSBs
• z: 26 middle bits
• y: 12 LSBs

For example, a 64-bit position can be broken down as follows:

Example value (big endian): 01000110000001110110001100 10110000010101101101001000 001100111111

• The red value is the X coordinate, which is 18357644 in this example.
  
• The blue value is the Z coordinate, which is -20882616 in this example.
  
• The green value is the Y coordinate, which is 831 in this example.
  

Encoded as follows:

((x & 0x3FFFFFF) << 38) | ((z & 0x3FFFFFF) << 12) | (y & 0xFFF)

And decoded as:

val = read_long();
x = val >> 38;
y = val << 52 >> 52;
z = val << 26 >> 38;

Note: The above assumes that the right shift operator sign extends the value (this is called an arithmetic shift), so that the signedness of the coordinates is preserved. In many languages, this requires the integer type of val to be signed. In the absence of such an operator, the following may be useful:

if x >= 1 << 25 { x -= 1 << 26 }
if y >= 1 << 11 { y -= 1 << 12 }
if z >= 1 << 25 { z -= 1 << 26 }

Fixed-point numbers

Some fields may be stored as fixed-point numbers, where a certain number of bits represents the signed integer part (number to the left of the decimal point) and the rest represents the fractional part (to the right). Floating points (float and double), in contrast, keep the number itself (mantissa) in one chunk, while the location of the decimal point (exponent) is stored beside it.

Essentially, while fixed-point numbers have lower range than floating points, their fractional precision is greater for higher values. This makes them ideal for representing global coordinates of an entity in Minecraft, as it's more important to store the integer part accurately than position them more precisely within a single block (or meter).

Coordinates are often represented as a 32-bit integer, where 5 of the least-significant bits are dedicated to the fractional part, and the rest store the integer part.

Java lacks support for fractional integers directly, but you can represent them as integers. To convert from a double to this integer representation, use the following formulas:

 abs_int = (int) (double * 32.0D);

And back again:

 double = (double) (abs_int / 32.0D);

Particle

Particle Name	Particle ID	Data
minecraft:ambient_entity_effect	0	None
minecraft:angry_villager	1	None
minecraft:block	2	Field Name Field Type Meaning BlockState VarInt The ID of the block state.
minecraft:block_marker	3	Field Name Field Type Meaning BlockState VarInt The ID of the block state.
minecraft:bubble	4	None
minecraft:cloud	5	None
minecraft:crit	6	None
minecraft:damage_indicator	7	None
minecraft:dragon_breath	8	None
minecraft:dripping_lava	9	None
minecraft:falling_lava	10	None
minecraft:landing_lava	11	None
minecraft:dripping_water	12	None
minecraft:falling_water	13	None
minecraft:dust	14	Field Name Field Type Meaning Red Float The red RGB value, between 0 and 1. Divide actual RGB value by 255. Green Float The green RGB value, between 0 and 1. Divide actual RGB value by 255. Blue Float The blue RGB value, between 0 and 1. Divide actual RGB value by 255. Scale Float The scale, will be clamped between 0.01 and 4.
minecraft:dust_color_transition	15	Field Name Field Type Meaning From Red Float The start red RGB value, between 0 and 1. Divide actual RGB value by 255. From Green Float The start green RGB value, between 0 and 1. Divide actual RGB value by 255. From Blue Float The start blue RGB value, between 0 and 1. Divide actual RGB value by 255. Scale Float The scale, will be clamped between 0.01 and 4. To Red Float The end red RGB value, between 0 and 1. Divide actual RGB value by 255. To Green Float The end green RGB value, between 0 and 1. Divide actual RGB value by 255. To Blue Float The end blue RGB value, between 0 and 1. Divide actual RGB value by 255.
minecraft:effect	16	None
minecraft:elder_guardian	17	None
minecraft:enchanted_hit	18	None
minecraft:enchant	19	None
minecraft:end_rod	20	None
minecraft:entity_effect	21	None
minecraft:explosion_emitter	22	None
minecraft:explosion	23	None
minecraft:gust	24	None
minecraft:gust_emitter	25	None
minecraft:sonic_boom	26	None
minecraft:falling_dust	27	Field Name Field Type Meaning BlockState VarInt The ID of the block state.
minecraft:firework	28	None
minecraft:fishing	29	None
minecraft:flame	30	None
minecraft:cherry_leaves	31	None
minecraft:sculk_soul	32	None
minecraft:sculk_charge	33	Field Name Field Type Meaning Roll Float How much the particle will be rotated when displayed.
minecraft:sculk_charge_pop	34	None
minecraft:soul_fire_flame	35	None
minecraft:soul	36	None
minecraft:flash	37	None
minecraft:happy_villager	38	None
minecraft:composter	39	None
minecraft:heart	40	None
minecraft:instant_effect	41	None
minecraft:item	42	Field Name Field Type Meaning Item Slot The item that will be used.
minecraft:vibration	43	Field Name Field Type Meaning Position Source Type VarInt The type of the vibration source (0 for `minecraft:block`, 1 for `minecraft:entity`) Block Position Position The position of the block the vibration originated from. Only present if Position Type is minecraft:block. Entity ID VarInt The ID of the entity the vibration originated from. Only present if Position Type is minecraft:entity. Entity eye height Float The height of the entity's eye relative to the entity. Only present if Position Type is minecraft:entity. Ticks VarInt The amount of ticks it takes for the vibration to travel from its source to its destination.
minecraft:item_slime	44	None
minecraft:item_snowball	45	None
minecraft:large_smoke	46	None
minecraft:lava	47	None
minecraft:mycelium	48	None
minecraft:note	49	None
minecraft:poof	50	None
minecraft:portal	51	None
minecraft:rain	52	None
minecraft:smoke	53	None
minecraft:white_smoke	54	None
minecraft:sneeze	55	None
minecraft:spit	56	None
minecraft:squid_ink	57	None
minecraft:sweep_attack	58	None
minecraft:totem_of_undying	59	None
minecraft:underwater	60	None
minecraft:splash	61	None
minecraft:witch	62	None
minecraft:bubble_pop	63	None
minecraft:current_down	64	None
minecraft:bubble_column_up	65	None
minecraft:nautilus	66	None
minecraft:dolphin	67	None
minecraft:campfire_cosy_smoke	68	None
minecraft:campfire_signal_smoke	69	None
minecraft:dripping_honey	70	None
minecraft:falling_honey	71	None
minecraft:landing_honey	72	None
minecraft:falling_nectar	73	None
minecraft:falling_spore_blossom	74	None
minecraft:ash	75	None
minecraft:crimson_spore	76	None
minecraft:warped_spore	77	None
minecraft:spore_blossom_air	78	None
minecraft:dripping_obsidian_tear	79	None
minecraft:falling_obsidian_tear	80	None
minecraft:landing_obsidian_tear	81	None
minecraft:reverse_portal	82	None
minecraft:white_ash	83	None
minecraft:small_flame	84	None
minecraft:snowflake	85	None
minecraft:dripping_dripstone_lava	86	None
minecraft:falling_dripstone_lava	87	None
minecraft:dripping_dripstone_water	88	None
minecraft:falling_dripstone_water	89	None
minecraft:glow_squid_ink	90	None
minecraft:glow	91	None
minecraft:wax_on	92	None
minecraft:wax_off	93	None
minecraft:electric_spark	94	None
minecraft:scrape	95	None
minecraft:shriek	96	Field Name Field Type Meaning Delay VarInt The time in ticks before the particle is displayed
minecraft:egg_crack	97	None
minecraft:dust_plume	98	None
minecraft:gust_dust	99	None
minecraft:trial_spawner_detection	100	None

BitSet

Represents Java's BitSet, a list of bits.

Field Name	Field Type	Meaning
Length	VarInt	Number of longs in the following array. May be 0 (if no bits are set).
Data	Array of Long	A packed representation of the BitSet as created by BitSet.toLongArray.

The nth bit in a BitSet is set when (longs[n/64] & (1L << (n % 64))) != 0, where n starts at 0.