CurseForge · Minecraft mod
RainAPI
Core library for RainJava featuring embedded ECJ compiler, Javassist bytecode tools, and ASM transformation pipeline. Enables dynamic Java compilation and class modification at runtime.
Quick answer
Which RainAPI release matches 1.20.1 Forge?
RainAPI-1.0.0.jar targets 1.20.1 with Forge. The project page does not say whether this file belongs on the client, dedicated server, or both. No extra mods listed for this file.
Where it goes
Is RainAPI required on the client, server, or both?
The project page does not say whether this file belongs on the client, dedicated server, or both.
The source does not explicitly classify this release as client-only or server-only.
What else does RainAPI-1.0.0.jar need?
RainAPI-1.0.0.jar on 1.20.1 Forge. Every mod below is checked against that same setup.
This file does not list any required mods. Do not add a library just because a different file uses it.
This file does not list any required or optional mods.
Before you install it
Add RainAPI without breaking your instance.
Built for RainAPI-1.0.0.jar on 1.20.1 Forge. Pick another file and the loader, install side or required mods may change.
- 01
Stick to this file
Use RainAPI-1.0.0.jar. It targets 1.20.1 with Forge; another release may have different loader, side or dependency requirements.
- 02
Bring the mods it needs
This file does not list any required mods. Do not add a library just because a different file uses it.
- 03
Put it on the correct side
The project page does not say whether this file belongs on the client, dedicated server, or both.
- 04
Pick the file you checked
Use the “Get this file” button beside RainAPI-1.0.0.jar. It opens that exact file at the source.
About this project
What does RainAPI add?
RainJava API
Advanced Runtime Class Transformation Framework
A foundational library providing Mixin and Coremod interoperability layers, powered by enterprise-grade bytecode and compilation tools.
Overview
RainJava API establishes the critical infrastructure for runtime class transformation pipelines. It serves as a middleware bridge between dynamic compilation workflows and Minecraft's standard modification systems (Mixin & Coremod), ensuring bytecode-level compatibility without compromising game stability.
While designed as the prerequisite foundation for the upcoming RainJava ecosystem, this API functions independently as a robust toolkit for developers requiring deep class manipulation capabilities.
Embedded Libraries
This mod ships with zero-external-dependency versions of industry-standard tools:
Javassist — High-level bytecode manipulation library for runtime class engineering
ECJ (Eclipse Compiler for Java) — Full-featured Java compiler capable of runtime source-to-bytecode transformation
JavaParser — Abstract Syntax Tree (AST) analysis and code generation framework
These libraries are shaded and isolated to prevent conflicts with other mods.
Technical Scope
Transformation Bridge — Facilitates communication between runtime-generated class definitions and established bytecode modification frameworks
Mixin Compatibility Layer — Enables standardized injection patterns to recognize and process dynamically provisioned classes
Coremod Integration — Provides stable hooks for runtime class definitions to participate in Forge's transformation chain
Sandboxed Execution — Implements security boundaries for runtime code evaluation environments
For Modders
Install this API if you:
Plan to develop for or use the upcoming RainJava framework
Require embedded Javassist/ECJ/JavaParser without bundling them yourself
Need stable Mixin/Coremod interoperability for advanced bytecode operations
Project description from CurseForge.
Pick your setup
RainAPI by Minecraft version and loader
Choose the version and loader you play, then open the matching release.
Check the dependencies, then try the file in a copied instance before changing a world you care about.
Recent files
RainAPI versions and loaders
RainAPI-1.0.0.jar
20 Feb 2026
Looking for an older file? The official CurseForge project page is in Resources.