DEVELOPER_API.md

Developer API

ViaFabricPlus exposes events and utility functions so other mods can integrate with it. If you want to include it in your project, keep in mind:

• Requires Java 25 (see jvm_version in gradle.properties)
• Needs a Fabric Loom setup (since it's a Minecraft mod, not a standalone API library)

Adding as a Dependency

If you only need the public API, include the viafabricplus-api artifact. If you also want to access internal features, use viafabricplus.

Kotlin (Gradle)

repositories {
    // https://github.com/ViaVersion/ViaFabricPlus/blob/ver/<version>/docs/DEVELOPER_API.md
    mavenCentral()
    maven("https://repo.viaversion.com")
}

dependencies {
    // Replace it with latest release
    runtimeOnly("com.viaversion:viafabricplus:x.x.x")
    compileOnly("com.viaversion:viafabricplus-api:x.x.x")
}

Groovy (Gradle)

repositories {
    mavenCentral()
    maven { name = "ViaVersion"; url = "https://repo.viaversion.com" }
}

dependencies {
    // Replace it with latest release
    runtimeOnly("com.viaversion:viafabricplus:x.x.x")
    compileOnly("com.viaversion:viafabricplus-api:x.x.x")
}

Using the API

Everything is reached through a single entry point:

final ViaFabricPlusAPI api = ViaFabricPlus.api();

ViaFabricPlusAPI is the only stable API surface other mods should use. Next to the mod's own metadata it hands out four sub-APIs:

• protocolTranslation() – the target version, per-connection versions, ViaVersion's UserConnection and a listener for version changes
• conversions() – translating items between Minecraft and ViaVersion, and dummy user connections
• limitations() – whether an item, enchantment, effect or banner pattern exists in a given version
• screens() – opening the mod's own screens

apiVersion() is incremented on every meaningful API change, so you can check what you're running against.

ViaFabricPlus.api().addChangeProtocolVersionListener((oldVersion, newVersion) -> {
    // Called whenever the target protocol version changes
});

ViaFabricPlus.getImpl() and ViaFabricPlusBase are deprecated for removal. Every method on it forwards to its replacement on ViaFabricPlusAPI, so migrating is a rename.

Entrypoint

Since your mod may load after ViaFabricPlus, hook into the loading cycle with a ViaFabricPlusEntrypoint declared in your fabric.mod.json under the viafabricplus key:

{
  "entrypoints": {
    "viafabricplus": [
      "com.example.ExampleEntrypoint"
    ]
  }
}

All of its methods are optional.

Custom Settings

api.settings() gives access to the mod's own groups and lets you register your own, which then show up as their own tab in the settings screen:

final SettingGroup group = ViaFabricPlus.api().settings().register("example_settings.example");

final BooleanSetting enabled = group.registerBoolean("enabled", true);
final VersionedBooleanSetting legacyOnly = group.registerVersionedBoolean("legacy_only", andOlder(v1_12_2), false);

The group and its settings are named by translation keys, so the example above needs example_settings.example and example_settings.example.enabled in your language files.

A VersionedBooleanSetting displays its version range in the screen, and its isActive() only returns true while the target version is inside that range.