Pre-release protocol

This page documents the changes from the last stable Minecraft release (currently 1.15.2, protocol 578) to the current pre-release (currently 20w12a, protocol 707). 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
0x4E 0x43	Spawn Position	Current	(unchanged)
0x43 0x44	Display Scoreboard	Current	(unchanged)
0x44 0x45	Entity Metadata	Current	(unchanged)
0x45 0x46	Attach Entity	Current	(unchanged)
0x46 0x47	Entity Velocity	Current	(unchanged)
0x47 0x48	Entity Equipment	Current	(unchanged)
0x48 0x49	Set Experience	Current	(unchanged)
0x49 0x4A	Update Health	Current	(unchanged)
0x4A 0x4B	Scoreboard Objective	Current	(unchanged)
0x4B 0x4C	Set Passengers	Current	(unchanged)
0x4C 0x4D	Teams	Current	(unchanged)
0x4D 0x4E	Update Score	Current	(unchanged)
Login clientbound
0x02	Login Success	Current	Pre

New/modified data types

No changes so far.

Entity Metadata

Abstract Arrow

Extends Entity.

Abstract base class for Tipped Arrow (which is used for regular arrows as well as tipped ones) and Spectral Arrow.

Index	Type	Meaning		Default
7	Byte	Bit mask	Meaning	0
		0x01	Is critical
		0x02	Is noclip (used by loyalty tridents when returning)
8	OptUUID	Unused		Empty
9 8	Byte	Peircing level		0

Tipped Arrow

Extends Abstract Arrow.

Used for both tipped and regular arrows. If not tipped, then color is set to -1 and no tipped arrow particles are used.

Index	Type	Meaning		Default
10 9	VarInt	Color (-1 for no particles)		-1

Spectral Arrow

Extends Abstract Arrow.

No additional metadata.

Trident

Extends Abstract Arrow.

Index	Type	Meaning		Default
10 9	VarInt	Loyalty level (enchantment)		0
11 10	Boolean	Has enchantment glint		False

Hoglin

Extends Animal.

No additional metadata.

Piglin

Extends Monster.

Index	Type	Meaning		Default
15	Boolean	Is baby		false
16	Boolean	Is immune to zombification		false
17	Boolean	Is charging crossbow		false

Zombie Pigman Zombified Piglin

Extends Zombie.

No additional metadata.

Block Actions

No changes so far.

Inventories

No changes so far.

Plugin Channels

No changes so far.

Play

Clientbound

No changes so far.

Serverbound

No changes so far.

Handshaking

Clientbound

There are no clientbound packets in the Handshaking state, since the protocol immediately switches to a different state after the client sends the first packet.

Serverbound

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 578 707)
			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. Note that SRV records are a complete redirect, e.g. if _minecraft._tcp.example.com points to mc.example.org, users connecting to example.com will provide mc.example.org as server address in addition to connecting to it.
			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

Status

Clientbound

No changes so far.

Serverbound

No changes so far.

Login

Clientbound

Login Success

Packet ID	State	Bound To	Field Name	Field Type	Notes
0x02	Login	Client		String (36) Int array	Unlike in other packets, this field contains the UUID as a string with hyphens a fixed length int array.
			Username	String (16)

This packet switches the connection state to play.

Serverbound

No changes so far.