Among Us Protocol Research

Note: This repo is outdated, it is correct up to and partially including the Airship Update. PRs are welcome!

Contained in this repo is my detailed explanation of the netcode behind Among Us, a game by Innersloth. Myself and others have spent countless hours scanning the game's decompiled source code as well as manually dissecting each and every packet sent by the game. Not all of this information will be correct, though it is safe to assume that almost all of it is, and those parts that I am uncertain of will be labeled as such.

I do not work for Innersloth, however Innersloth has provided support in the construction of this wiki; for the most part this is just the result of an obsession in discovering how the game works.

This repo does not currently contain instructions on how to decompile/deobfuscate the game.

To intercept packets, I recommend using Wireshark with one of the display filters below.

To show all game traffic:
udp.port in { 22023 22123 22223 22323 22423 22523 22623 22723 22823 22923 }

To show only reliable packets (recommended as movement, pings, and acks can add a bunch of noise):
udp.port in { 22023 22123 22223 22323 22423 22523 22623 22723 22823 22923 } and data[0] == 01

If you would like to discuss the Among Us protocol or client modding with me or others interested in such topics, you are welcome to join the NodePolus Discord server, or Reactor

Table of Contents

1. Packet Structure
   1. Protocol Data Types
   2. Packed Integers
   3. The Structure of a Hazel Message
   4. The Vector2 Type
   5. Packet Types (SendOption)
      1. 0x00 Normal
      2. 0x01 Reliable
      3. 0x08 Hello
      4. 0x09 Disconnect
      5. 0x0a Acknowledgement
      6. 0x0b Fragment
      7. 0x0c Ping
   6. Enums
      1. AlterGameTag
      2. ChatNoteType
      3. Color
      4. DisconnectReason
      5. GameKeyword
      6. GameOverReason
      7. GameState
      8. Hat
      9. KillDistance
      10. LimboState
      11. Map
      12. Pet
      13. QuickChatMode
      14. ReportOutcome
      15. ReportReason
      16. Skin
      17. SpawnFlag
      18. SpawnType
      19. SystemType
      20. TaskBarMode
      21. TaskType
   7. The Different Types of IDs
2. Root Message Types
   1. 0x00 HostGame
   2. 0x01 JoinGame
   3. 0x02 StartGame
   4. 0x03 RemoveGame
   5. 0x04 RemovePlayer
   6. 0x05 GameData
   7. 0x06 GameDataTo
   8. 0x07 JoinedGame
   9. 0x08 EndGame
   10. 0x09 GetGameList
   11. 0x0a AlterGame
   12. 0x0b KickPlayer
   13. 0x0c WaitForHost
   14. 0x0d Redirect
   15. 0x0e ReselectServer
   16. 0x10 GetGameListV2
   17. 0x11 ReportPlayer
3. GameData and GameDataTo Message Types
   1. 0x01 Data
   2. 0x02 RPC
   3. 0x04 Spawn
   4. 0x05 Despawn
   5. 0x06 SceneChange
   6. 0x07 Ready
   7. 0x08 ChangeSettings
   8. 0xcd ClientInfo
4. RPC Message Types
   1. 0x00 PlayAnimation
   2. 0x01 CompleteTask
   3. 0x02 SyncSettings
   4. 0x03 SetInfected
   5. 0x04 Exiled
   6. 0x05 CheckName
   7. 0x06 SetName
   8. 0x07 CheckColor
   9. 0x08 SetColor
   10. 0x09 SetHat
   11. 0x0a SetSkin
   12. 0x0b ReportDeadBody
   13. 0x0c MurderPlayer
   14. 0x0d SendChat
   15. 0x0e StartMeeting
   16. 0x0f SetScanner
   17. 0x10 SendChatNote
   18. 0x11 SetPet
   19. 0x12 SetStartCounter
   20. 0x13 EnterVent
   21. 0x14 ExitVent
   22. 0x15 SnapTo
   23. 0x16 Close
   24. 0x17 VotingComplete
   25. 0x18 CastVote
   26. 0x19 ClearVote
   27. 0x1a AddVote
   28. 0x1b CloseDoorsOfType
   29. 0x1c RepairSystem
   30. 0x1d SetTasks
   31. 0x1f ClimbLadder
   32. 0x20 UsePlatform
5. InnerNetObject Types
   1. SkeldShipStatus
   2. MeetingHud
   3. LobbyBehaviour
   4. GameData
   5. PlayerControl
   6. MiraShipStatus
   7. PolusShipStatus
   8. DleksShipStatus
   9. VoteBanSystem
   10. PlayerPhysics
   11. CustomNetworkTransform
6. The SystemType Implementations
   1. ReactorSystem
   2. SwitchSystem
   3. LifeSuppSystem
   4. MedScanSystem
   5. SecurityCameraSystem
   6. HudOverrideSystem
   7. AutoDoorsSystem
   8. SabotageSystem
   9. HqHudSystem
   10. DeconSystem
   11. DoorsSystem
7. Miscellaneous
   1. The Structure of the GameOptionsData Object
   2. Converting Game IDs to and from Game Codes
   3. Reading the Client Version
   4. Map-Specific IDs for Vents and Tasks
      1. The Skeld
         1. Vents
         2. Tasks
      2. MIRA HQ
         1. Vents
         2. Tasks
      3. Polus
         1. Vents
         2. Tasks
      4. The Airship
         1. Vents
         2. Tasks
         3. Ladders