Since 1.21, enchantments has been data-driven, which means you should define them in data-packs, instead of in the codes. Please see Enchantment definition Minecraft page for details.

To use the enchantments in code, you should just store RegistryKey objects of the enchantment.

TutorialEnchantments

public final class TutorialEnchantments {
  public static final RegistryKey<Enchantment> FROST = of("frost");
 
  private static RegistryKey<Enchantment> of(String name) {
    return RegistryKey.of(RegistryKeys.ENCHANTMENT, Identifier.of("tutorial", name));
  }
 
  public static void initialize() {
  }
}

Remember to refer to the initialize method in your ModInitializer:

ExampleMod

public class ExampleMod implements ModInitializer {
  // [...]
 
  @Override
  public void onInitialize() {
    // [...]
    TutorialEnchantments.initialize();
  }
}

To add a translated name for your enchantment, see the bottom of the tutorial.

This part of the tutorial only applies to older Minecraft versions.

To add enchantments to your mod, you'll need to:

• create a class that extends Enchantment or another existing Enchantment (such as DamageEnchantment)
• register your enchantment
• add custom functionality or mechanics if needed
• add translations for your enchantment ¹⁾

Enchantments can either have custom functionality implemented separately (such as smelting ores mined) or can use already existing mechanics (such as DamageEnchantment), which are applied when appropriate. The base Enchantment class also has several methods to create functionality, such as an “on enemy hit” method.

Our new enchantment is called Frost and slows mobs on hit. The slowness effect, durability, and potency will grow relative to the level of the enchantment. In our enchantment class, we pass up UNCOMMON as the enchantment rarity, WEAPON as the enchantment target, and MAINHAND as the only valid tool type for our enchantment.

public class FrostEnchantment extends Enchantment {
    public FrostEnchantment() {
        super(Enchantment.Rarity.UNCOMMON, EnchantmentTarget.WEAPON, new EquipmentSlot[] {EquipmentSlot.MAINHAND});
    }
}

We will now override a few basic methods for basic functionality:

getMinPower is related to the minimum level needed to see the enchant in a table, but it is not a 1:1 ratio. Most enchantments return something like 10 * level, with different scales depending on the max level and rarity of the enchantment. We will return 1 so it is always available. Note that the max power of an enchantment is set to min(level) + 5 by default, which means this enchantment will only appear at very low levels. You will have to tweak your enchantment properties on your own and look at similar enchantment values to find the sweet number spot.

@Override
public int getMinPower(int level) {
    return 1;
}

getMaxLevel is the number of levels the enchantment has. Sharpness has a max level of 5. ²⁾

@Override
public int getMaxLevel() {
    return 3;
}

Finally, we will implement our slowness effect in the onTargetDamage method, which is called when you whack an enemy with a tool that has your enchantment.

@Override
public void onTargetDamaged(LivingEntity user, Entity target, int level) {
    if(target instanceof LivingEntity livingEntity) {
        livingEntity.addStatusEffect(new StatusEffectInstance(StatusEffects.SLOWNESS, 20 * 2 * level, level - 1));
    }
 
    super.onTargetDamaged(user, target, level);
}

If the entity we are hitting can have status effects (LivingEntitys can have status effects, but not Entity), give it the slowness effect. The duration of the effect is 2 seconds per level, and the potency is equivalent to the level.

The final enchantment file should look like this.

public class FrostEnchantment extends Enchantment {
    public FrostEnchantment() {
        super(Enchantment.Rarity.UNCOMMON, EnchantmentTarget.WEAPON, new EquipmentSlot[] {EquipmentSlot.MAINHAND});
    }
 
    @Override
    public int getMinPower(int level) {
        return 1;
    }
 
    @Override
    public int getMaxLevel() {
        return 3;
    }
 
    public void onTargetDamaged(LivingEntity user, Entity target, int level) {
        if(target instanceof LivingEntity) {
            ((LivingEntity) target).addStatusEffect(new StatusEffectInstance(StatusEffects.SLOWNESS, 20 * 2 * level, level - 1));
        }
 
        super.onTargetDamaged(user, target, level);
    }
}

Registering enchantments follows the same process as usual:

public class ExampleMod implements ModInitializer {
    public static Enchantment FROST = new FrostEnchantment();
 
    @Override
    public void onInitialize() {
        Registry.register(Registries.ENCHANTMENT, new Identifier("tutorial", "frost"), FROST);
    }
}

Note: In practice, if you have many enchantments, it is better to place them in a separate class. Here we did all things in ModInitializer for simplicity.

This registers our enchantment under the namespace tutorial:frost. All non-treasure enchantments are available in an enchanting table, including the ones you register.

This part works both versions since 1.21 and before 1.21.

You'll need to add a translation to your enchantment as well. Head over to your mod lang file and add a new entry:

resources/data/tutorial/lang/en_us.json

{
    "enchantment.tutorial.frost": "Frost"
}

If you go in-game, you should be able to enchant main hand weapons with your new enchant.