Use 3.4.0 for Minecraft 1.7.9/.7.2/1.6.4/1.6.2/1.5.2/1.4.7 and older

Users of MCPC-Plus 1.7.2 and above should look for a special build (ProtocolLib - MCPC 1.7.2) on my Jenkins server. Cauldron users should download ProtocolLib - Cauldron.

Users of the new 1.8 build of Spigot should download "ProtocolLib - Spigot Hack 1.8" on my Jenkins server.

Certain tasks are impossible to perform with the standard Bukkit API, and may require working with and even modify Minecraft directly. A common technique is to modify incoming and outgoing packets, or inject custom packets into the stream. This is quite cumbersome to do, however, and most implementations will break as soon as a new version of Minecraft has been released, mostly due to obfuscation.

Critically, different plugins that use this approach may hook into the same classes, with unpredictable outcomes. More than often this causes plugins to crash, but it may also lead to more subtle bugs.

Up-to-date developer builds of this project can be acquired at my Jenkins server. These builds have not been approved by the BukkitDev staff. Use them at your own risk.


Please create a ticket with as much information as possible if you experience a problem that has not already been reported. Comments with a huge stack trace will be deleted.

If you need help with the API, please use the developer support forum. If your question cannot be made public for whatever reason (including security bugs), send me a personal message instead.

For server operators

Just download ProtocolLib from the link above. It doesn't do anything on its own, it simply allows other plugins to function.


  • Why do I get FieldAccessExceptions when I try to read or write from packets?

The reason for these exceptions is because ProtocolLib is not using the packet format as described on the Wiki, it's using the in-memory representation of these packets. Often, the in-memory representation will use integers instead of shorts and bytes, and store more complex objects (like ItemStacks) directly.

You can figure out the in-memory representation from the Minecraft source code, or just use PacketWrapper where I've done all that work for you.


Source code for a bunch of example programs that use ProtocolLib can be found at this thread on the main support forum.

You may also be interested in PacketWrapper, a library that makes it possible to modify a packet without having to decompile the Minecraft source code.

Finally, for the more advanced users who want to use ProtocolLib if present, but still fall back on their own packet listening system, I recommend taking a look at this thread. I explain where and how to inject code into CraftBukkit in order to intercept sent and received packets yourself.

Maven repository

If you're using Maven, you'll be able to automatically download the JAR, JavaDoc and associated sources from the following repository:

    <name>Comphenix Repository</name>
<!-- And so on -->

This repository contains ProtocolLib, TagHelper and BlockPatcher. You can add any of them as a dependency like so:




Main administrative command. Supports the following sub-commands:

  • config: Reload the configuration file.
  • check: Check for new versions on BukkitDev.
  • update: Check for new versions and automatically download the JAR. The server must be restarted for this to take effect.
  • timings: Toggle measuring the amount of CPU time spent by each plugin. See here for more information.
  • listeners: Display what plugins are using ProtocolLib, and the packet types they are intercepting.

All of these commands require the permission protocol.admin.


/protocol update


Add or remove a debug packet listener. This is useful for plugin authors who just wants to see when a packet is sent, and with what content.

Sub commands:

  • add: Add a packet listener with a given packet ID.
  • remove: Remove one or every packet listener with the given packet IDs.
  • names: Print the name of every given packet ID.

Parameters (in order):

  1. Connection side: Either client or server.
  2. Multiple ID ranges: Can be a single packet ID like 14, or a range like 10 - 15. Defaults to 0 - 255 if not specified.
  3. Detailed: If TRUE, prints the full packet content.


/packet add client 10-13 true

For 3.0.0 and above, you should specify the protocol, sender and name instead:

/packet add play server chat true

In 3.4.0-SNAPSHOT and above, you can also display the packet before its modified by any packet listeners:

/packet add play server chat compare

Remove all listeners:

/packet remove client
/packet remove server

Note that this command should rarely be used on a production server. Listening to too many packets may crash the server.


The filter system (introduced in 2.4.1) uses the built in JavaScript interpreter in JVM 6 (Rhino) to extend the packet command with filtering capabilities - it is now possible to, say, only print entity metadata packet events (packet add server 40) for a given entity ID:

> packet add server 40 true
Added listener ListeningWhitelist{priority=MONITOR, packets=[40]}
> filter add entity_filter 40
Enter filter program ('}' to complete or CANCEL):
function(event, packet) {
>   return packet.a == 1000; 
Added filter entity_filter.

This should be much more convenient than having to compile a test plugin and reload the whole server. Note that this feature is disabled by default for security reasons. To enable it, add "debug: true" to config.yml.


A small set of configuration options are available:

Global section



auto updater.notifytrueInform any player with the permission when a new version of ProtocolLib is out.
auto updater.downloadtrueAutomatically download and install the newest version of ProtocolLib. The installation will take effect when the server restarts.
auto updater.delay43200The number of seconds between each check for a new update.
auto updater.last0This simply records the last time (in seconds since 01.01.1970) an update check was performed. Set it to 0 to force a new update check.
metricstrueIf TRUE, ProtocolLib will publish anonymous usage data to Set it to FALSE to opt-out.
background compilertrueIf TRUE, ProtocolLib will try and improve performance by replacing reflection with compiled code on-the-fly.
ignore version checkNoneForce ProtocolLib to start for a specified Minecraft version, even if it is incompatible.
suppressed reportsNoneIf any error or warning report is present in this list, they will not appear in the console or the log.

For more information, take a look at the default configuration file.

Tutorial for developers

See this page for more information.


One of the main goals of this project was to achieve maximum compatibility with CraftBukkit. And the end result is quite good - in tests I successfully ran an unmodified ProtocolLib on CraftBukkit 1.8.0, and it should be resilient against future changes. It's likely that I won't have to update ProtocolLib for anything but bug and performance fixes.

How is this possible? It all comes down to reflection in the end. Essentially, no name is hard coded - every field, method and class is deduced by looking at field types, package names or parameter types. It's remarkably consistent across different versions.

Plugins that appear to be compatible

Plugins known to be compatible

  • SpoutPlugin

Plugins using ProtocolLib

Inactive projects

Please let me know if you want me to add your plugin to this list. :)


This plugin uses MCStats to generate and publish anonymous aggregate usage statistics, but you can easily opt-out by setting metrics in config.yml to false.

If enabled, the following is sent every ten minutes:

  • Metrics revision version (currently 6).
  • Server's GUID
  • Players currently online (not max player count)
  • Server version string (the same version string you see in /version)
  • Current version of ProtocolLib
  • The name of every plugin that registers a packet listener in ProtocolLib.


I would like to thank everyone who has donated to ProtocoLib. I really appreciate it. :)



ProtocolLib Statistics

Note: Create a ticket if you're having problems. Don't post stack traces in the comments.

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  • Avatar of rourke750 rourke750 Oct 29, 2014 at 00:54 UTC - 0 likes

    Hey so I have this class and what is meant to happen is it changes the packets that clients shouldnt be able to see like health, potion effects, armor, ect and it works correctly. The problem is when groups of players get near each other this error is thrown:

  • Avatar of ThisUsernameIsMine ThisUsernameIsMine Oct 21, 2014 at 14:29 UTC - 0 likes

    @ShooterMC: Go

    Make sure online-mode=true in, unless you don't see any player names at all, then it could be a different issue ;-)

    Last edited Oct 21, 2014 by ThisUsernameIsMine
  • Avatar of games647 games647 Oct 18, 2014 at 11:07 UTC - 0 likes

    @aadnk: Go

    Could you add ScoreboardStats to the "Plugins using ProtocolLib" list?

    Thank you for this awesome plugin, it's very helpful.

  • Avatar of sanjay900 sanjay900 Oct 12, 2014 at 02:12 UTC - 0 likes

    @ShooterMC: Go

    Are you using a plugin that modifies the tab list in any way? I had this problem using TabAPI

  • Avatar of ShooterMC ShooterMC Oct 09, 2014 at 19:40 UTC - 0 likes

    So strange... I use the protocollib version for 1.8 and makes plugins work, but the tablist doesn't appear to work, no players appear on it :S


  • Avatar of aadnk aadnk Oct 05, 2014 at 20:01 UTC - 0 likes

    @libraryaddict: Go

    Sure, no problem.

    @raphy123: Go

    You could try updating TagAPI, but I don't know if it works for the 1.8 compatible build of Spigot.

  • Avatar of libraryaddict libraryaddict Oct 05, 2014 at 10:36 UTC - 0 likes

    Mind updating your maven repo?

    I can't resolve profile.getUUID() as it stands


  • Avatar of raphy123 raphy123 Oct 05, 2014 at 10:24 UTC - 0 likes


    i have this error with version 1.8 of spigot

  • Avatar of aadnk aadnk Sep 30, 2014 at 12:05 UTC - 0 likes

    @killyouslow: Go

    The 1.8 protocol build? Use ProtocolLib - Spigot 1.8 Compatible.

    @CommodoreAlpha: Go

    MCPC+ was renamed to Cauldron, so you should use ProtocolLib - Cauldron.

    @DanSpedey: Go

    It's too early to tell. Very little of Sponge has actually been implemented, so I can't say just how feasable or easy it would be to port it.

    It's a promising project, but it's not given that it will become the new leading Minecraft server implementation. Other projects may get there first.

  • Avatar of CommodoreAlpha CommodoreAlpha Sep 30, 2014 at 03:38 UTC - 0 likes

    Sorry if this is a silly question, but which build number on your Jenkins offered the special MCPC+ support again?

    Sure, I'd love to include my server IP here. But it's under construction, and I wouldn't want to get sued for players wandering inside and getting hit by a random beam of steel floating about. And no, I doubt plugins would make very good lawyers either. I've never seen a plugin that forced you to sign a contract do so well.


Date created
Oct 05, 2012
Last update
Jun 15, 2014
Development stage
  • enUS
GNU General Public License version 2 (GPLv2)
Curse link
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