Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.20.4, protocol 765) to the current pre-release (currently 23w51b, protocol Snapshot 170). 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
Play clientbound
0x71	Update Attributes	Current	Pre
0x72	Entity Effect	Current	Pre

New/modified data types

No changes so far.

Entity Metadata

Type (VarInt Enum)	Value (Varies)	Notes
0	Byte
1	VarInt
2	VarLong
3	Float
4	String
5	Chat
6	OptChat (Boolean + Chat)	Chat is present if the Boolean is set to true
7	Slot
8	Boolean
9	Rotation	3 Floats: rotation on x, rotation on y, rotation on z
10	Position
11	OptPosition (Boolean + Position)	Position is present if the Boolean is set to true
12	Direction (VarInt)	(Down = 0, Up = 1, North = 2, South = 3, West = 4, East = 5)
13	OptUUID (Boolean + UUID)	UUID is present if the Boolean is set to true
14	BlockID (VarInt)
15	OptBlockID (VarInt)	0 for absent (implies air); otherwise, a block state ID as per the block state registry
16	NBT
17	Particle
18	Villager Data	3 VarInts: villager type, villager profession, level
19	OptVarInt	0 for absent; 1 + actual value otherwise. Used for entity IDs.
20	Pose	A VarInt enum: 0: STANDING, 1: FALL_FLYING, 2: SLEEPING, 3: SWIMMING, 4: SPIN_ATTACK, 5: SNEAKING, 6: LONG_JUMPING, 7: DYING, 8: CROAKING, 9: USING_TONGUE, 10: SITTING, 11: ROARING, 12: SNIFFING, 13: EMERGING, 14: DIGGING
21	Cat Variant	A VarInt that points towards the CAT_VARIANT registry.
22	Frog Variant	A VarInt that points towards the FROG_VARIANT registry.
23	OptGlobalPos (Boolean + GlobalPos)	GlobalPos consists of a dimension identifier and Position.
24	Painting Variant	A VarInt that points towards the PAINTING_VARIANT registry.
25	Sniffer State	A VarInt enum: IDLING = 0, FEELING_HAPPY = 1, SCENTING = 2, SNIFFING = 3, SEARCHING = 4, DIGGING = 5, RISING = 6
26	Armadillo State	A VarInt enum: IDLE = 0, ROLLING = 1, SCARED = 2
26 27	Vector3	3 Floats: x, y, z
27 28	Quaternion	4 Floats: x, y, z, w

Armadillo

Extends Animal.

Index	Type	Meaning		Default
17	Armadillo State	Armadillo State		IDLE

Block Actions

No changes so far.

Inventories

No changes so far.

Plugin Channels

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.

Configuration

Clientbound

No changes so far.

Serverbound

No changes so far.

Play

Clientbound

Update Attributes

Sets attributes on the given entity.

Packet ID	State	Bound To	Field Name		Field Type		Notes
0x71	Play	Client	Entity ID		VarInt
			Number Of Properties		VarInt		Number of elements in the following array.
			Property	Key Id	Array	Identifier VarInt Enum	See below.
				Value		Double	See below.
				Number Of Modifiers		VarInt	Number of elements in the following array.
				Modifiers		Array of Modifier Data	See Attribute#Modifiers. Modifier Data defined below.

Known Key values (see also Attribute#Modifiers):

Id	Key	Default	Min	Max	Label
0	generic.armor	0.0	0.0	30.0	Armor.
1	generic.armor_toughness	0.0	0.0	20.0	Armor Toughness.
2	generic.attack_damage	2.0	0.0	2048.0	Attack Damage.
3	generic.attack_knockback	0.0	0.0	5.0	Attack Knockback.
4	generic.attack_speed	4.0	0.0	1024.0	Attack Speed.
5	generic.block_interaction_range	4.5	0.0	64.0	Block Interaction Range.
6	generic.entity_interaction_range	3.0	0.0	64.0	Entity Interaction Range.
7	generic.flying_speed	0.4	0.0	1024.0	Flying Speed.
8	generic.follow_range	32.0	0.0	2048.0	Follow Range.
9	horse.jump_strength	0.7	0.0	2.0	Jump Strength.
10	generic.knockback_resistance	0.0	0.0	1.0	Knockback Resistance.
11	generic.luck	0.0	-1024.0	1024.0	Luck.
12	generic.max_absorption	0.0	0.0	2048.0	Max Absorption.
13	generic.max_health	20.0	1.0	1024.0	Max Health.
14	generic.movement_speed	0.7	0.0	1024.0	Movement Speed.
15	generic.scale	1.0	0.0625	16.0	Scale.
16	zombie.spawn_reinforcements	0.0	0.0	1.0	Spawn Reinforcements Chance.
17	generic.step_height	0.6	0.0	10.0	Step Height.

Modifier Data structure:

Field Name	Field Type	Notes
UUID	UUID
Amount	Double	May be positive or negative.
Operation	Byte	See below.

The operation controls how the base value of the modifier is changed.

• 0: Add/subtract amount
• 1: Add/subtract amount percent of the current value
• 2: Multiply by amount percent

All of the 0's are applied first, and then the 1's, and then the 2's.

Entity Effect

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x72	Play	Client	Entity ID	VarInt
			Effect ID	VarInt	See this table.
			Amplifier	Byte	Notchian client displays effect level as Amplifier + 1.
			Duration	VarInt	Duration in ticks. (-1 for infinite)
			Flags	Byte	Bit field, see below.
			Has Factor Data	Boolean	Used in DARKNESS effect
			Factor Codec	NBT Tag	See below

	The following information needs to be added to this page:
	What exact effect does the blend bit flag have on the client?

Within flags:

• 0x01: Is ambient - was the effect spawned from a beacon? All beacon-generated effects are ambient. Ambient effects use a different icon in the HUD (blue border rather than gray). If all effects on an entity are ambient, the "Is potion effect ambient" living metadata field should be set to true. Usually should not be enabled.
• 0x02: Show particles - should all particles from this effect be hidden? Effects with particles hidden are not included in the calculation of the effect color, and are not rendered on the HUD (but are still rendered within the inventory). Usually should be enabled.
• 0x04: Show icon - should the icon be displayed on the client? Usually should be enabled.
• 0x08: Blend - ???

Factor Data

Name	Type	Notes
padding_duration	TAG_INT
factor_start	TAG_FLOAT
factor_target	TAG_FLOAT
factor_current	TAG_FLOAT
effect_changed_timestamp	TAG_INT
factor_previous_frame	TAG_FLOAT
had_effect_last_tick	TAG_BOOLEAN

Serverbound

No changes so far.