Mappings

Default mappings

• Fabric (pre-26.x): Official Mojang mappings via Loom's officialMojangMappings()
• Fabric (26.x+): No mappings needed. Minecraft is unobfuscated. Prism sets fabric.loom.disableObfuscation=true automatically.
• NeoForge / Forge (1.17+): Official mappings via ModDevGradle / ForgeGradle 7
• Forge 1.16.5 (forge16): MCP mappings via ForgeGradle 6 (snapshot / 20210309-1.16.5 by default)
• Legacy Forge (1.7.10–1.12.2): MCP mappings via RetroFuturaGradle (stable / 39 by default)

Yarn mappings

Fabric projects can use Yarn mappings instead of Mojang mappings:

fabric {
    loaderVersion = "0.18.6"
    yarn("1.21.1+build.3")
}

When yarn() is set, Prism uses net.fabricmc:yarn:{version}:v2 instead of officialMojangMappings(). Yarn is only available for obfuscated versions (pre-26.x).

Unobfuscated versions (26.x+)

Starting from Minecraft 26.1 (1.21.11), the game ships with unobfuscated source. This means:

• No intermediary mappings are used
• No remapping is applied to mod JARs
• Loom's officialMojangMappings() is not called (would throw an error)
• Fabric dependencies use implementation instead of modImplementation (no remapping needed)
• Access wideners still work (they widen access levels and mutability, not related to obfuscation)
• Mixin refmaps use static remapping

Prism handles all of this automatically based on the Minecraft version. You do not need to configure anything differently for 26.x.

Parchment

Parchment adds parameter names and Javadoc to Mojang mappings. Only applicable to obfuscated versions (pre-26.x).

version("1.21.1") {
    parchmentMinecraftVersion = "1.21.1"
    parchmentMappingsVersion = "2024.07.28"

    fabric {
        loaderVersion = "0.18.6"
    }
    neoforge {
        loaderVersion = "21.1.222"
    }
}

Both parchmentMinecraftVersion and parchmentMappingsVersion must be set. If only one is provided, Parchment is skipped with a warning.

LexForge mappings

LexForge (ForgeGradle 7, Forge 1.21.1+) supports official Mojang mappings, Parchment, and custom channels. See Loaders — LexForge mappings for configuration details. The prismDoctor output shows the resolved channel as fg7 official, fg7 parchment, or fg7 <channel>.

Forge 1.16.5 mappings (forge16)

forge16 (ForgeGradle 6) uses MCP mappings. 1.16.5 has no stable channel, so the default is snapshot / 20210309-1.16.5. Override with an explicit channel/version:

version("1.16.5") {
    forge16 {
        loaderVersion = "36.2.42"
        mappings("snapshot", "20210309-1.16.5")
    }
}

Parchment is not wired for forge16. The prismDoctor output shows the resolved channel as fg6 <channel>.

Common project compilation

The common subproject compiles against vanilla Minecraft. Prism resolves the correct artifact automatically:

Minecraft version	Artifact	Source
1.20.2+	NeoForm (net.neoforged:neoform)	NeoForge Maven
1.20.1 and older	MCP (de.oceanlabs.mcp:mcp_config)	NeoForge Maven

For older versions where NeoForm does not exist, Prism falls back to MCP and uses MDG Legacy in vanilla mode.

The resolved NeoForm version is cached in ~/.gradle/caches/prism/neoform-versions.txt for 24 hours. Delete this file to force a refresh. If you're offline, set the version manually:

version("1.20.1") {
    neoFormVersion = "1.20.1-20230612.114412"
    // ...
}