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Version 2.3
A library for patching, replacing and decorating
.NET and Mono methods during runtime.


Harmony gives you an elegant and high level way to alter the functionality in applications written in C#. It works great in games and is well established in titles like

7 Days To Die
Stardew Valley
Oxygen Not Included
Kerbal Space Program
Slime Rancher

and others like Ravenfield, Sheltered, Staxel, The Ultimate Nerd Game, Total Miner, Unturned, SCP: Secret Laboratory ...

It is also used in unit testing WPF controls at Microsoft and Google and in many other areas.

How it works

If you develop in C# and your code is loaded as a module/plugin into a host application, you can use Harmony to alter the functionality of all the available assemblies of that application. Where other patch libraries simply allow you to replace the original method, Harmony goes one step further and gives you:

• A way to keep the original method intact
• Execute your code before and/or after the original method
• Modify the original with IL code processors
• Multiple Harmony patches co-exist and don't conflict with each other
• Works at runtime and does not touch any files


If you want a single file, dependency-merged assembly, you should use the Lib.Harmony nuget package. This is the preferred way.

If you instead want to supply the dependencies yourself, you should use the Lib.Harmony.Thin nuget package. You get more control but you are responsible to make all references available at runtime.


Please check out the documentation and join the official discord server.


I put thousands of hours into this project and its support. So every little action helps:

• Become a GitHub sponsor or a Patreon
• Upvote this stackoverflow answer
• Spread the word in your developer communities

This project uses the great MonoMod.Core library by 0x0ade and nike4613.

Harmony 1

Harmony 1 is deprecated and not under active development anymore. The latest version of it (v1.2.0.1) is stable and contains only minor bugs. Keep using it if you are in an environment that exclusively uses Harmony 1. Currently Harmony 1.x and 2.x are NOT COMPATIBLE with each other and SHOULD NOT BE MIXED. The old documentation can still be found at the Wiki.