Java Edition protocol

Minecraft: Java Edition is one of the two editions of Minecraft known for being written in Java and depends on the Minecraft Launcher to download, update, and play. Most of the new development projects focus on either creating entirely new programs from scratch that interoperate with Minecraft (such as a bot or server) or modding projects that integrate with the game's client or server and provide bug fixes, new features, and several enhancements to existing features.

Documentation

There are ongoing efforts to keep reverse engineered documentation updated, but it isn't as easy as it sounds. The protocol generally changes slightly with each release. Below are links to the current documentation segments, which may or may not be completely up to date.

Protocol

• Protocol FAQ
  • Normal login sequence for a client
  • Normal ping sequence to a server
• Current protocol specification
  • Data types
  • Server List Ping
  • Encryption
  • Plugin channels
  • Registry data
  • Command data
  • Chat
  • Inventory
  • Slot data
  • Chunk format
  • Block actions
  • Object data
  • Entity metadata
  • Entity statuses
  • Particles
• Development version protocol specification
• Protocol version numbers^[vg]
• Protocol history^[vg]
• Proxies^[vg]
• Minecraft Forge handshake specification^[vg]

Minecraft APIs

• Authentication systems – Minecraft have used multiple authentication systems in the past:
  • Microsoft authentication – the current authentication system based on Microsoft account and Xbox Live.
  • Yggdrasil – the second authentication system based on legacy Mojang account.
  • Legacy Minecraft authentication – the first authentication system based on legacy Minecraft account.
• Mojang API – several legacy and current APIs for querying player data and make changes programmatically.
• Game files^[vg]
• Realms API^[vg]

Map format

• Map Format Specification^[vg]
  • Region Files^[vg]

Vanilla implementation

• Client command line arguments
• Debugging^[vg]
• Data Generators^[vg]

Miscellaneous

• Data formats – several data formats used by Minecraft to store data readable by machines or humans:
  • NBT^[vg]/NBT format^[main] – a tree data structure and binary data format used by Minecraft in many save files to store arbitrary data.
  • JSON – a human-readable data interchange formats used by the game in many data-driven definitions of an object in resource pack and data pack.
• Text formatting and styling – several resources on Minecraft's rendering of text:
  • Font – changes how characters look in the game defined by resource pack.
  • Text component – the modern way to define text formatting, such as italic, bold, strike through, colors, and other types of formatting in Minecraft.
  • Formatting codes – the legacy way to define text formatting based on "§" character.
• Server protocols and APIs:
  • RCON
  • Query
  • Minecraft Server Management Protocol

Tools and mods

• Clients - third-party Java Edition clients
• Servers^[vg] - third-party Java Edition servers
• Libraries^[vg] - libraries to interface with Minecraft data files or network protocols
• Utilities^[vg] - tools that interface with a client, server, or data files, such as proxies, bots, or inventory editors
• Wrappers^[vg] - mods that override features in the client or server
• Generators^[vg] - tools that extract data from Mojang to a readable format
• Decompilers^[vg] - tools for decompiling Java Edition
• Burger - a tool that generates information for arbitrary Java Edition versions
  • Pokechu22's fork - where new version development is mostly done
  • Burger Vitrine - shows differences in data and protocol between arbitrary versions
  • PAaaS - shows differences in protocol and sounds for newer versions (1.8 and above)
• Code Snippets^[vg]

Communities

• Minecraft Protocol (via Discord)
• #mcdevs (via irc.libera.chat).

For more info, see the Java Edition protocol category.