Data Generation: Language Files (MultiLoader 1.21+)

Until now the mod's translation strings have lived in a hand-written en_us.json file. This tutorial replaces that file with a NeoForge LanguageProvider so all translation keys are generated - keeping them consistent with your Java registries and catching typos at compile time.

NOTE

Complete the Data Generation: Advancements tutorial before continuing. We add a new provider to the existing gatherData method.

Delete the Existing Lang File

Before running datagen you must remove the hand-written lang file so the generated one is not merged with stale entries. Delete:

text

common/src/main/resources/assets/examplemod/lang/en_us.json

Datagen will write a fresh copy to the generated resources directory, which the build already places on the resource-pack lookup path.

Language Provider

In your NeoForge data package, create ExampleLangProvider extending LanguageProvider. The superclass constructor takes the pack output, your mod ID, and the target locale:

java

public class ExampleLangProvider extends LanguageProvider {
    public ExampleLangProvider(PackOutput output) {
        super(output, Constants.MOD_ID, "en_us");
    }
    @Override
    protected void addTranslations() {
        // translation entries go here
    }
}

The locale string ("en_us") determines the output file name. Datagen writes the result to assets/<modid>/lang/<locale>.json.

Adding Translations

LanguageProvider ships typed helpers for the most common registry objects. The addItem and addBlock variants accept a Supplier, so you can pass your DeferredHolder references directly - no .get() needed. For keys that have no dedicated helper (creative tabs, sound subtitles, advancement text) use the generic add(String key, String value) overload:

java

@Override
protected void addTranslations() {
    // Items - addItem(Supplier<? extends Item>, String)
    addItem(ItemRegistry.IRON_STICK,       "Iron Stick");
    addItem(ItemRegistry.TOMATO,           "Tomato");
    addItem(ItemRegistry.EXAMPLE_SWORD,    "Example Sword");
    addItem(ItemRegistry.EXAMPLE_PICKAXE,  "Example Pickaxe");
    addItem(ItemRegistry.EXAMPLE_AXE,      "Example Axe");
    addItem(ItemRegistry.EXAMPLE_SHOVEL,   "Example Shovel");
    addItem(ItemRegistry.EXAMPLE_HOE,      "Example Hoe");
    addItem(ItemRegistry.EXAMPLE_HELMET,   "Example Helmet");
    addItem(ItemRegistry.EXAMPLE_CHESTPLATE, "Example Chestplate");
    addItem(ItemRegistry.EXAMPLE_LEGGINGS, "Example Leggings");
    addItem(ItemRegistry.EXAMPLE_BOOTS,    "Example Boots");
    // Blocks - addBlock(Supplier<? extends Block>, String)
    addBlock(BlockRegistry.NEW_DIRT,        "New Dirt");
    addBlock(BlockRegistry.EXAMPLE_BE_BLOCK, "Example Block Entity Block");
    // Creative tabs, subtitles, advancements - no dedicated helper, use add()
    add("itemGroup.examplemod.items",  "Example Mod Items");
    add("itemGroup.examplemod.blocks", "Example Mod Blocks");
    add("subtitles.examplemod.example_ambient", "Example ambient sound");
    add("advancements.examplemod.root.title",               "Example Mod");
    add("advancements.examplemod.root.description",         "Begin your journey with Example Mod.");
    add("advancements.examplemod.get_iron_stick.title",     "A New Tool");
    add("advancements.examplemod.get_iron_stick.description", "Pick up an Iron Stick.");
    add("advancements.examplemod.place_new_dirt.title",     "Breaking Ground");
    add("advancements.examplemod.place_new_dirt.description", "Place a New Dirt block.");
}

TIP

Other typed helpers include addEntityType(Supplier<EntityType<?>>, String), addEnchantment(Supplier<Enchantment>, String), and addEffect(Supplier<MobEffect>, String). Each resolves the registry key for you so the translation key always stays in sync with the registered name.

Multiple Languages

To ship more than one language, create a separate LanguageProvider subclass per locale and register each one independently. Only the locale string passed to super() changes:

java

public class ExampleLangProviderFrench extends LanguageProvider {
    public ExampleLangProviderFrench(PackOutput output) {
        super(output, Constants.MOD_ID, "fr_fr");
    }
    @Override
    protected void addTranslations() {
        addItem(ItemRegistry.IRON_STICK, "Bâton de fer");
        addBlock(BlockRegistry.NEW_DIRT, "Nouvelle terre");
        // ... remaining entries
    }
}

Each provider writes its own independent JSON file. You do not need to repeat keys that Minecraft would fall back to - any key missing from a non-English file falls back to en_us automatically in vanilla.

NOTE

For this tutorial series we only generate en_us. The French class above is shown for illustration only - you don't need to create it.

Registering the Provider

Language files are client-side assets, so use event.includeClient() rather than event.includeServer():

java

@SubscribeEvent
public static void gatherData(GatherDataEvent event) {
    DataGenerator generator = event.getGenerator();
    PackOutput output = generator.getPackOutput();
    // ... existing providers ...
    generator.addProvider(
            event.includeClient(),
            new ExampleLangProvider(output));
}

Running Datagen

Run NeoForge Data. The generated file appears at:

text

common/src/generated/resources/assets/examplemod/lang/en_us.json

Open it and verify every key from the deleted hand-written file is present. Launch the game and confirm item names, block names, creative tab labels, and advancement text all display correctly.

TIP

If you see untranslated keys in-game (raw strings like item.examplemod.iron_stick) it usually means either the generated file wasn't included in the resource pack path or the datagen run failed silently - check the run console for errors.

You can find the source for this tutorial here:

View Source on GitHub

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Custom Entities (MultiLoader 1.21+)

Register an EntityType, create a PathfinderMob subclass with wandering and look-at goals, wire up attribute registration on both loaders, add a client-only renderer using a vanilla model, register a colour-tinted spawn egg, and generate entity loot tables.

Continue →