Plugin ASM
by laolizhennui
Plugin ASM is a Java Agent library for Paper, Bukkit and Folia servers that lets other code modify bytecode at runtime through simple annotations.
What it does
The library works as a lightweight, Mixin-style bytecode injection framework. Developers declare method modifications with annotations, and the changes are applied through ASM instead of being written by hand as bytecode. Reflection, inheritance and a runtime performance penalty are described by the author as not required, and the library is aimed at server environments such as Paper and Folia.
Plugin ASM is server-side only, so only the server needs it and players join without installing anything. It is published as a Java Agent for 1.21.11, with the latest file 0.1.0-alpha3 on the alpha channel, and game versions 1.0 – 1.21.11 are covered across 98 release versions. The project is released under the GNU Lesser General Public License v2.1 or later and is open source, with public links to the source code, issue tracker and wiki, where usage examples are kept.
The author describes the project as young and notes known limitations that may be addressed in later versions. Contributions are welcomed through the repository, and the wiki holds detailed usage examples and the scenarios the library has been tested against.
Key features
Annotation-driven injection
Bytecode changes to arbitrary classes are declared with annotations and applied at runtime.
Mixin-style method changes
Method modifications are declared in a Mixin-like style, so the injection points are written next to the code they change.
ASM-based bytecode writing
The library uses ASM for the bytecode work, and developers can still write bytecode manually where needed.
Paper and Folia support
The framework is designed for Paper and Folia server environments and works alongside Bukkit-based plugins.
Gallery
Compatibility
Latest build for each game version and loader.
1.21.x12 of 12 versions with builds
1.20.x7 of 7 versions with builds
1.19.x5 of 5 versions with builds
1.18.x3 of 3 versions with builds
1.17.x2 of 2 versions with builds
1.16.x6 of 6 versions with builds
1.15.x3 of 3 versions with builds
1.14.x5 of 5 versions with builds
1.13.x3 of 3 versions with builds
1.12.x2 of 2 versions with builds
Only full game releases are shown. This mod publishes no snapshot builds.
50 older game versions (1.0 – 1.12) not shown. All files on Modrinth
Use cases
Plugin developers
Developers who need to change server code that has no API hook can inject their changes without reflection.
Server maintainers testing changes
Maintainers evaluating a runtime change can use the wiki examples to see how a modification is declared.
Who it’s for: Plugin developers working on Paper or Folia servers who want declarative bytecode modification. Server owners do not need to do anything beyond installing the agent on the server.
Questions
Does Plugin ASM have to be installed on players' clients?
Which Java version does Plugin ASM need?
Where can usage examples be found?
In the catalog
Plugin ASM is one of 3,514 Library mods on ModsFinder. 19,862 mods support Minecraft 1.21.11.
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What the author says
PASM 是一个轻量级、Mixin 风格的字节码注入框架，专为 Paper / Folia 服务端设计。 它允许你通过简单的注解，在运行时修改任意类的字节码——无需反射，无需继承，无性能损耗。 PASM is a lightweight, Mixin‑style bytecode injection framework designed specifically for Paper / Folia server environments. It allows you to modify the bytecode of arbitrary classes at runtime using simple annotations—no…
Official listing
- Modrinth page
- modrinth.com/mod/plugin-asm
- Owner
- laolizhennui
- Published
- 2026-02-13
- Updated on Modrinth
- 2026-02-18
- Facts verified
- 2026-10-15