Plugin channels

Plugin channels allow client mods and server plugins to communicate without cluttering up chat. This post by Dinnerbone is a good introduction and basic documentation.

Definitions

Data Types

PathEntity

Represents calculated path of entity.

Name	Type	Notes
Current path index	{{#switch: Plugin channels	Data types = Int	#default = Int }}	Index in the points array that the entity is currently targeting.
Target	PathPoint
Number of points	{{#switch: Plugin channels	Data types = Int	#default = Int }}	Number of elements in the following array
Points array	{{#switch: Plugin channels	Data types = Array	#default = Array }} of PathPoint	The actual points on the path
Open set length	{{#switch: Plugin channels	Data types = Int	#default = Int }}	Number of elements in the following array
Open set	{{#switch: Plugin channels	Data types = Array	#default = Array }} of PathPoint
Closed set length	{{#switch: Plugin channels	Data types = Int	#default = Int }}	Number of elements in the following array
Closed set	{{#switch: Plugin channels	Data types = Array	#default = Array }} of PathPoint

You can read more here[1].

PathPoint

Represents single point in path

Name	Type	Notes
X	{{#switch: Plugin channels	Data types = Int	#default = Int }}
Y	{{#switch: Plugin channels	Data types = Int	#default = Int }}
Z	{{#switch: Plugin channels	Data types = Int	#default = Int }}
Distance from origin	{{#switch: Plugin channels	Data types = Float	#default = Float }}
Cost	{{#switch: Plugin channels	Data types = Float	#default = Float }}
Cost malus	{{#switch: Plugin channels	Data types = Float	#default = Float }}	Number that is rendered
Has been visited	{{#switch: Plugin channels	Data types = Boolean	#default = Boolean }}
Node type	{{#switch: Plugin channels	Data types = Int	#default = Int }} {{#switch: Plugin channels	Data types = Enum	#default = Enum }}	See below
Distance to target	{{#switch: Plugin channels	Data types = Float	#default = Float }}

Values for node type:

• 0: BLOCKED
• 1: OPEN
• 2: WALKABLE
• 3: TRAPDOOR
• 4: FENCE
• 5: LAVA
• 6: WATER
• 7: WATER_BORDER
• 8: RAIL
• 9: DANGER_FIRE
• 10: DAMAGE_FIRE
• 11: DANGER_CACTUS
• 12: DAMAGE_CACTUS
• 13: DANGER_OTHER
• 14: DAMAGE_OTHER
• 15: DOOR_OPEN
• 16: DOOR_WOOD_CLOSED
• 17: DOOR_IRON_CLOSED
• 18: BREACH
• 19: LEAVES
• 20: STICKY_HONEY
• 21: COCOA

Reserved channels

minecraft:register

Two-way

Allows the client or server to register for one or more custom channels, indicating that data should be sent on those channels if the receiving end supports it too. Payload is a null (0x00) separated list of strings.

This channel was renamed from REGISTER in 1.13.

minecraft:unregister

Two-way

Allows the client or server to unregister from one or more custom channels, indicating that the receiving end should stop sending data on those channels. Payload is a null-separated list of strings. This is only useful if plugins are disabled/unloaded while the client is connected.

This channel was renamed from UNREGISTER in 1.13.

Channels internal to Minecraft

Since 1.3, Minecraft itself uses several plugin channels to implement new features. These internal channels use the minecraft namespace. They are not formally registered using the register channel. The vanilla Minecraft server will send these packets regardless, and the vanilla client will accept them.

Note that there were originally more channels included, but most of these were removed in 1.13. See this revision of the article for the original list. As of 1.14, the only remaining channels other than the brand one are debugging-related channels, which are not normally sent.

minecraft:brand

Two-way

For version 1.12.2(protocol version 340) and below, channel name is: MC|Brand

Announces the server and client implementation name right after a player has logged in. For the Notchian client and server, this is "vanilla" (which is chosen using the function net.minecraft.client.ClientBrandRetriever.getClientModName() and encoded as a UTF-8 string).

These brands are used in crash reports and a few other locations. It's recommended that custom clients and servers use their own brand names for the purpose of identification (for the Notchian client, the class used to get the brand is one of the few non-obfuscated classes). The brand is not processed in any other way, and Notchian clients will connect to servers with different brands with no issue (the brand is not used to validate).

The Notchian server sends a minecraft:brand packet right after it sends a Login (play) packet, and the Notchian client sends it right after receiving a Login (play) packet. However, some modified clients and servers will not send this packet (or will take longer to send it than normal), so it is important to not crash if the brand has not been sent. Additionally, the brand may change at any time (for instance, if connected through a BungeeCord instance, you may switch from a server with one brand to a server with another brand without receiving a Login (play) packet).

minecraft:debug/path

Server to client

What appears to be the purpose of minecraft:debug/path as seen in the snapshot 16w14a announcement. This is not found in the normal game.

Never sent, but does something with pathfinding debugging. The client reads the data and stores it, but its renderer cannot be enabled without modifications.

Name	Type	Notes
Unknown 1	{{#switch: Plugin channels	Data types = Int	#default = Int }}	Used as a key in the mapping that stores this data; might be an entity ID?
Unknown 2	{{#switch: Plugin channels	Data types = Float	#default = Float }}	Appears to be the "radius" of the squares for each pathpoint
Entity	PathEntity	See Data Types above

PathEntity's index point is rendered red; the others are rendered blue. PathEntity's target PathPoint is rendered as a green cube. PathPoint's closed set is rendered red, and open set is rendered green.

minecraft:debug/neighbors_update

Server to client

Never sent, but used to debug block updates. Does not render without modifying the client.

Name	Type	Notes
Time	{{#switch: Plugin channels	Data types = VarLong	#default = VarLong }}	World timestamp at which the update occurred. 200 ticks after this timestamp, the given update stops rendering.
Location	{{#switch: Plugin channels	Data types = Position	#default = Position }}	Location of the block that updated.

minecraft:debug/structures

Server to client

Never sent, but (presumably) used to debug structures. Does not render without modifying the client.

Adds a single new structure, which will always be rendered if the player is in the same dimension.

Field name		Field type		Notes
Dimension		{{#switch: Plugin channels		Data types = Int	#default = Int }}	The dimension the structure is in.
Bounding box minX		{{#switch: Plugin channels		Data types = Int	#default = Int }}	Main box for the structure (rendered in white). min must be less than max
Bounding box minY		{{#switch: Plugin channels		Data types = Int	#default = Int }}
Bounding box minZ		{{#switch: Plugin channels		Data types = Int	#default = Int }}
Bounding box maxX		{{#switch: Plugin channels		Data types = Int	#default = Int }}
Bounding box maxY		{{#switch: Plugin channels		Data types = Int	#default = Int }}
Bounding box maxZ		{{#switch: Plugin channels		Data types = Int	#default = Int }}
Count		{{#switch: Plugin channels		Data types = Int	#default = Int }}	Number of elements in the following array
Sub-boxes	Bounding box minX	{{#switch: Plugin channels	Data types = Array	#default = Array }}	{{#switch: Plugin channels	Data types = Int	#default = Int }}	min must be less than max
	Bounding box minY		{{#switch: Plugin channels	Data types = Int	#default = Int }}
	Bounding box minZ		{{#switch: Plugin channels	Data types = Int	#default = Int }}
	Bounding box maxX		{{#switch: Plugin channels	Data types = Int	#default = Int }}
	Bounding box maxY		{{#switch: Plugin channels	Data types = Int	#default = Int }}
	Bounding box maxZ		{{#switch: Plugin channels	Data types = Int	#default = Int }}
	Flag		{{#switch: Plugin channels	Data types = Boolean	#default = Boolean }}	If true, the sub-box is rendered in green, otherwise in blue.

minecraft:debug/worldgen_attempt

Server to client

Never sent, but (presumably) used to debug something with world generation. Does not render without modifying the client.

Adds a colored cube of the list of things to render. This cube is never removed.

Field name	Field type	Notes
Location	{{#switch: Plugin channels	Data types = Position	#default = Position }}	The center of the location to render.
Size	{{#switch: Plugin channels	Data types = Float	#default = Float }}	Diameter/side length of a cube to render.
Red	{{#switch: Plugin channels	Data types = Float	#default = Float }}	Red value to render, from 0.0 to 1.0.
Green	{{#switch: Plugin channels	Data types = Float	#default = Float }}	Green value to render, from 0.0 to 1.0.
Blue	{{#switch: Plugin channels	Data types = Float	#default = Float }}	Blue value to render, from 0.0 to 1.0.
Alpha	{{#switch: Plugin channels	Data types = Float	#default = Float }}	Alpha value to render, from 0.0 to 1.0.

minecraft:debug/poi_ticket_count

Server to client

Never sent, but used to set amount of free tickets for POI

Field name	Field type
Location of POI	{{#switch: Plugin channels	Data types = Position	#default = Position }}
Num of tickets	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}

minecraft:debug/poi_added

Server to client

Never sent, but used to add debugging POI. Does not render without modifying the client.

Field name	Field type	Notes
Location	Positon	Location of POI
POI Type	{{#switch: Plugin channels	Data types = String	#default = String }} (x)	Type of POI, see the POI article
Tickets	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}	Amount of free tickets

minecraft:debug/poi_removed

Server to client

Never sent, but used to remove debugging POI. Does not render without modifying the client.

Field name	Field type	Notes
Location	Positon	Location of POI

minecraft:debug/village_sections

Server to client

Never sent, but used to add/remove debugging VilliageSections. Does not render without modifying the client.

Field name	Field type	Notes
Num of VillageSection locations to be added	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}	Number of VillageSection locations in following fields.
Location of VillageSection	{{#switch: Plugin channels	Data types = Array	#default = Array }} of {{#switch: Plugin channels	Data types = Position	#default = Position }}	Locations of VillageSections
Num of VillageSection locations to be removed	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}	Number of VillageSection locations in following fields.
Location of VillageSection	{{#switch: Plugin channels	Data types = Array	#default = Array }} of {{#switch: Plugin channels	Data types = Position	#default = Position }}	Locations of VillageSections

minecraft:debug/goal_selector

Server to client

Never sent, but (presumably) used to debug goal selectors. Does not render without modifying the client.

Adds multiple lines of text on the given location, spaced by 0.25 units upward on the Y-axis.

Field name		Field type		Notes
Location		{{#switch: Plugin channels		Data types = Position	#default = Position }}	The location of the goal selector.
Unknown		{{#switch: Plugin channels		Data types = Int	#default = Int }}	Key for the goal selector mapping, possibly entity ID.
Count		{{#switch: Plugin channels		Data types = Int	#default = Int }}	Number of elements in the following array.
Goals	Priority	{{#switch: Plugin channels	Data types = Array	#default = Array }}	{{#switch: Plugin channels	Data types = Int	#default = Int }}	Currently unused
	Is running		{{#switch: Plugin channels	Data types = Boolean	#default = Boolean }}	Defines the color of the text. #00FF00 if true, #CCCCCC otherwise
	Name		{{#switch: Plugin channels	Data types = String	#default = String }} (255)

minecraft:debug/brain

Server to client

Never sent. Used to debug villager's brain. Doesn't render without modifying the client.

Field name	Field type	Notes
X	{{#switch: Plugin channels	Data types = Double	#default = Double }}	X coordinate of villager's position
Y	{{#switch: Plugin channels	Data types = Double	#default = Double }}	Y coordinate of villager's position
Z	{{#switch: Plugin channels	Data types = Double	#default = Double }}	Z coordinate of villager's position
Unique ID	{{#switch: Plugin channels	Data types = UUID	#default = UUID }}	Villager's Unique ID
Entity ID	EID	Villager's Entity ID
Name	{{#switch: Plugin channels	Data types = String	#default = String }} (x)	Villager's name
Profession	{{#switch: Plugin channels	Data types = String	#default = String }} (x)	Villager's profession
XP	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}	Villager's experience points
Inventory	{{#switch: Plugin channels	Data types = String	#default = String }} (x)	Villager's inventory (need more research on that)
Has path	{{#switch: Plugin channels	Data types = Boolean	#default = Boolean }}	Indicates whether the next field is Path
Path	PathEntity	Movement path
Wants golem	{{#switch: Plugin channels	Data types = Boolean	#default = Boolean }}	Indicates whether the villager in need of Golem.

minecraft:debug/bee

Server to client

Never sent, but (presumably) used to debug bee pathfinding to hives and flowers. Does not render without modifying the client.

Field name	Field type	Notes
X	{{#switch: Plugin channels	Data types = Double	#default = Double }}	X coordinate of rendering location
Y	{{#switch: Plugin channels	Data types = Double	#default = Double }}	Y coordinate of rendering location
Z	{{#switch: Plugin channels	Data types = Double	#default = Double }}	Z coordinate of rendering location
Unique ID	{{#switch: Plugin channels	Data types = UUID	#default = UUID }}	Bee's unique ID
EID	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}	EID of the Bee
Has hive position	{{#switch: Plugin channels	Data types = Boolean	#default = Boolean }}	True if following field value is location of bee hive.
Location of hive	{{#switch: Plugin channels	Data types = Position	#default = Position }}	Optional position of bee hive.
Has flower position	{{#switch: Plugin channels	Data types = Boolean	#default = Boolean }}	True if following field value is location of flower.
Location of flower	{{#switch: Plugin channels	Data types = Position	#default = Position }}	Optional position of flower.
Travel ticks	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}	Purpose unknown.
Has path	{{#switch: Plugin channels	Data types = Boolean	#default = Boolean }}	True if following field value is path.
Path	PathEntity	Serialized path.
Num of goals	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}	Number of goals in following fields.
Goal	{{#switch: Plugin channels	Data types = Array	#default = Array }} of {{#switch: Plugin channels	Data types = String	#default = String }} (x)	Probably string name of goal
Num of blacklisted hives	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}	Number of blacklisted hives in following fields.
Blacklisted hive	{{#switch: Plugin channels	Data types = Array	#default = Array }} of {{#switch: Plugin channels	Data types = Position	#default = Position }}	Position of blacklisted hive.

minecraft:debug/hive

Server to client

Never sent, but (presumably) used to debug hives. Does not render without modifying the client.

Field name	Field type	Notes
Location	{{#switch: Plugin channels	Data types = Position	#default = Position }}	Rendering location. If a player is more than 30 blocks away, rendering is skipped.
Hive type	{{#switch: Plugin channels	Data types = String	#default = String }}	Name of hive type
Occupant count	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}	Number of bees inside this hive
Honey level	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}	Level of honey inside this hive
Sedated	{{#switch: Plugin channels	Data types = Boolean	#default = Boolean }}	True if bees are sedated, false otherwise
Last seen	{{#switch: Plugin channels	Data types = VarLong	#default = VarLong }}	Never used in debug renderer?

minecraft:debug/game_test_add_marker

Server to client

Never sent, but used to set different debug markers in the world. Does not render for vanilla clients below version 1.16.5.

Field name	Field type	Notes
Location	{{#switch: Plugin channels	Data types = Position	#default = Position }}	Location of the marker.
Color	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}	Encoded ARGB color (Read below about encoding).
Name	{{#switch: Plugin channels	Data types = String	#default = String }} (x)	Name of marker
Lifetime	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}	Time in milliseconds, after which the marker will be destroyed

Color can be encoded as following:

int encoded = 0;
encoded = encoded | ((int) blueChannel);
encoded = encoded | ((int) greenChannel << 8);
encoded = encoded | ((int) redChannel << 16);
encoded = encoded | ((int) alphaChannel << 24);
return encoded;

Note that color is normalized by client.

minecraft:debug/game_test_clear

Clears all debug markers.

minecraft:debug/raids

Server to client

Never sent, but used to set debug raid centers. Does not render without modifying the client.

Field name	Field type	Notes
Num of locations	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}	Number of locations provided by following array
Locations	{{#switch: Plugin channels	Data types = Array	#default = Array }} of {{#switch: Plugin channels	Data types = Position	#default = Position }}	Locations of raid centers

minecraft:debug/game_event

Server to client

Never sent, but used to debug game events. Does not render without modifying the client.

Field name	Field type	Notes
Game event identifier	{{#switch: Plugin channels	Data types = String	#default = String }} (x)
Game event location	{{#switch: Plugin channels	Data types = Position	#default = Position }}

minecraft:debug/game_event_listeners

Server to client

Never sent, but used to track game event listeners. Does not render without modifying the client.

Field name	Field type	Notes
Position source type	{{#switch: Plugin channels	Data types = Identifier	#default = Identifier }}
Listener data	{{#switch: Plugin channels	Data types = Byte Array	#default = Byte Array }}
Listener range	{{#switch: Plugin channels	Data types = VarInt	#default = VarInt }}

Position source type	{{#switch: Plugin channels	Data types = Identifier	#default = Identifier }}	Data
Block position source	minecraft:block	Data contain single block position
Entity position source	minecraft:entity	Data contain single EID

MC|PingHost

Client to server

Sent after a Server list ping in Minecraft 1.6. More information on Server List Ping#1.6. In 1.7 and above, the Request (Status, 0x00, serverbound) packet is instead sent before the ping.

Since this plugin channel is only sent for the legacy server list ping, it uses the older packet structure.

Notable community plugin channels

Channels listed in this section are not used by the vanilla Minecraft client or server. This is just a likely-incomplete list of channels used by mods/plugins popular within the Minecraft community.

bungeecord:main

Formerly BungeeCord; additionally, note that the channel name is remapped by spigot so that the old name can still be used in plugins.

See here

fml:handshake, fml:play

Main article: Minecraft Forge Handshake

Previously FML|HS, FML

Used by Minecraft Forge to negotiate required mods, among other things. fml:handshake and fml:play

ML|OpenTE

Server to client

Used by ModLoader to support custom GUI windows. Does not use the REGISTER channel.

WECUI

Main article: /WorldEditCUI

Used by the server-side WorldEdit and the client-side WorldEditCUI to coordinate selections.

wdl:init, wdl:control, wdl:request

Main article: /World downloader

Used by the client-side World Downloader mod to get permission information and perform permission requests.

world_info, world_id, worldinfo:world_id

Used by VoxelMap and JourneyMap (1.16.5+) to query the world ID, which is useful on BungeeCord-style server networks to keep maps unique.