Kotlin for Forge Mod FAQ
20 questions players actually ask, answered.
What does Kotlin for Forge actually do?
It bundles the Kotlin runtime and language libraries so that mods written in Kotlin can load and run on Forge. Without it, any Kotlin-based mod will fail to start or crash on launch.
Do I need to install Kotlin for Forge if I don't have any Kotlin mods?
No, it does nothing on its own and only matters when another mod depends on it. If no mod requires it, you can leave it out.
How do I know which of my mods needs Kotlin for Forge?
Check the crash log or the mod list for a missing dependency error naming Kotlin for Forge. The mod that triggered it is the one that requires it.
My game crashes on startup saying Kotlin for Forge is missing. What do I do?
Add Kotlin for Forge to your modpack alongside the mod that needs it, and make sure both are for the same Minecraft version. The crash log will name the mod that's asking for it.
Can I have multiple versions of Kotlin for Forge installed at once?
No, only one version should be present in your mods folder. Having duplicates or mismatched versions causes conflicts and launch failures.
Will Kotlin for Forge slow down my game or hurt performance?
It's a lightweight library and generally has negligible impact on performance. Any lag you see is almost always from the Kotlin mods using it, not the library itself.
Is Kotlin for Forge compatible with other mod loaders like Fabric or NeoForge?
No, it's built specifically for the Forge mod loader. Fabric and NeoForge have their own separate Kotlin support, so don't mix them.
How do I update Kotlin for Forge without breaking my modpack?
Update it only when a mod requires a newer version, and match the version to your Minecraft version. Back up your modpack first, since a mismatch can cause crashes.
Two Kotlin mods are conflicting. Is that Kotlin for Forge's fault?
Usually not; the conflict is between the mods themselves. Make sure Kotlin for Forge is up to date and that both mods support the same Minecraft version.
Does Kotlin for Forge need any configuration or setup after installing?
No, it works out of the box once placed in the mods folder. There are no settings to change; just keep it updated with your other mods.
What does the Kotlin for Forge Mod do?
It is a compatibility library that lets Minecraft mods written in the Kotlin programming language run on the Forge mod loader. It bundles the necessary Kotlin libraries and provides a language provider to load Kotlin mods.
Do I need Kotlin for Forge to play Minecraft?
No, it is a library mod, so you only need it if another mod you use requires it to work correctly. For regular players it acts as a dependency mod.
Which mod loaders does Kotlin for Forge support?
It supports Forge and NeoForge.
Which Minecraft versions does Kotlin for Forge support?
The project lists support for Minecraft 1.21.10, 1.21.11, 26.1, 26.1.1, 26.1.2, and 26.2.
Does Kotlin for Forge add new items or blocks?
No, it is a library mod that adds a Kotlin language loader and optional utilities for developers, not new items or blocks.
What Kotlin libraries does Kotlin for Forge bundle?
As of Kotlin for Forge 1.8.0, it provides Kotlin 1.4.21, Kotlin coroutines 1.4.2, Kotlin JSON serialization 1.0.1, and Jetbrains annotations 20.1.0.
What is KotlinLanguageProvider in Kotlin for Forge?
It is a language provider that loads @Mod object declarations, allowing mods written in Kotlin to be loaded.
What is AutoKotlinEventBusSubscriber in Kotlin for Forge?
It loads @EventBusSubscriber declarations, letting developers use special declarations for event subscribers.
Does Kotlin for Forge have its own event bus?
Yes, as of 1.2.0 it provides its own implementation of IEventBus that supports IEventBus#addListener and IEventBus#addGenericListener with function references.
Do I have to use the Kotlin language loader to use Kotlin for Forge?
No, you do not have to use the language loader or any of the features Kotlin for Forge provides; you can just use it for the bundled Kotlin libraries.