Developing Minecraft Fabric Mods

Standard Fabric mod structure (1.21.1, Java 21):

Java
// src/main/java/com/example/examplemod/ExampleMod.java
package com.example.examplemod;

import net.fabricmc.api.ModInitializer;
import net.minecraft.core.registries.Registries;
import net.minecraft.resources.ResourceLocation;
import net.minecraft.world.item.BlockItem;
import net.minecraft.world.item.Item;
import net.minecraft.world.level.block.Block;
import net.minecraft.world.level.block.state.BlockBehaviour;
import net.minecraft.world.level.material.MapColor;
import com.mojang.serialization.MapCodec;

public class ExampleMod implements ModInitializer {
    public static final String MOD_ID = "examplemod";

    public static final Block EXAMPLE_BLOCK = new Block(
        BlockBehaviour.Properties.of()
            .mapColor(MapColor.STONE)
            .strength(3.0f, 3.0f)
            .requiresCorrectToolForDrops()
    );

    @Override
    public void onInitialize() {
        var blockId = ResourceLocation.fromNamespaceAndPath(MOD_ID, "example_block");
        var registeredBlock = net.minecraft.core.Registry.register(
            net.minecraft.core.registries.BuiltInRegistries.BLOCK, blockId, EXAMPLE_BLOCK
        );
        net.minecraft.core.Registry.register(
            net.minecraft.core.registries.BuiltInRegistries.ITEM, blockId,
            new BlockItem(registeredBlock, new Item.Properties())
        );
    }
}

fabric.mod.json entrypoint must reference com.example.examplemod.ExampleMod.

Progress checklist for any new mod feature:

• Confirm Minecraft version, mapping (Yarn/Mojmap), loom version, Java version (17 for ≤1.20.4, 21 for ≥1.20.5/1.21.x)
• Register content (block/item/entity) in ModInitializer
• Add lang file (assets/<modid>/lang/en_us.json)
• Add block/item model JSON (assets/<modid>/models/block/ and models/item/)
• Add blockstate JSON if block has variants
• Add texture PNG (assets/<modid>/textures/block/ or textures/item/), size must be power of 2 (16x16, 32x32...)
• Add loot table if block should drop itself (data/<modid>/loot_table/blocks/)
• Build with ./gradlew build and check for errors before delivering
• Verify no missing texture (purple/black checker) by cross-checking every model references an existing PNG path

Version/Java mapping (critical, never mix these up):

*If a version number looks non-standard (e.g. "1.21.11"), assume the user means the latest stable 1.21.x and confirm which exact patch (1.21, 1.21.1, 1.21.4...) since mappings differ per patch — ask for clarification only if registry/API calls actually differ between patches, otherwise default to 1.21.1 conventions.

Example 1: Input: "Basit bir custom item ekle, sağ tıklayınca can versin." Output:

Java
public static final Item HEALING_APPLE = new Item(new Item.Properties().food(
    new FoodProperties.Builder().nutrition(4).saturationModifier(0.3f).build()
));

Registered via Registry.register(BuiltInRegistries.ITEM, ResourceLocation.fromNamespaceAndPath(MOD_ID, "healing_apple"), HEALING_APPLE); Model: assets/modid/models/item/healing_apple.json → {"parent": "item/generated", "textures": {"layer0": "modid:item/healing_apple"}} Texture: 16x16 PNG at assets/modid/textures/item/healing_apple.png.

Example 2: Input: "Blockstate ekle, block'un 4 yöne bakması lazım (facing)." Output:

JSON
{
  "variants": {
    "facing=north": { "model": "modid:block/example_block" },
    "facing=south": { "model": "modid:block/example_block", "y": 180 },
    "facing=east":  { "model": "modid:block/example_block", "y": 90 },
    "facing=west":  { "model": "modid:block/example_block", "y": 270 }
  }
}

Plus Java: implement HorizontalDirectionalBlock, override getStateForPlacement and createBlockStateDefinition.