Mob Effects 1.20.4

Learn how to add custom mob effects.

WARNING

This page is written for version 1.20.4. Documentation for older versions may be incomplete.

Mob effects, also known as status effects or simply effects, are a condition that can affect an entity. They can be positive, negative or neutral in nature. The base game applies these effects in various ways such as food, potions etc.

The /effect command can be used to apply effects on an entity.

Custom Mob Effects

In this tutorial we'll add a new custom effect called Tater which gives you one experience point every game tick.

Extend MobEffect

Let's create a custom effect class by extending MobEffect, which is the base class for all effects.

public class TaterEffect extends MobEffect {
	protected TaterEffect() {
		// category: StatusEffectCategory - describes if the effect is helpful (BENEFICIAL), harmful (HARMFUL) or useless (NEUTRAL)
		// color: int - Color is the color assigned to the effect (in RGB)
		super(MobEffectCategory.BENEFICIAL, 0xe9b8b3);
	}

	// Called every tick to check if the effect can be applied or not
	@Override
	public boolean shouldApplyEffectTickThisTick(int duration, int amplifier) {
		// In our case, we just make it return true so that it applies the effect every tick
		return true;
	}

	// Called when the effect is applied
	@Override
	public void applyEffectTick(LivingEntity entity, int amplifier) {
		if (entity instanceof Player) {
			((Player) entity).giveExperiencePoints(1 << amplifier); // Higher amplifier gives you experience faster
		}
	}
}

Registering Your Custom Effect

Similar to block and item registration, we use Registry.register to register our custom effect into the MOB_EFFECT registry. This can be done in our initializer.

public class ExampleModEffects implements ModInitializer {
	public static final MobEffect TATER_EFFECT = new TaterEffect();

	@Override
	public void onInitialize() {
		Registry.register(BuiltInRegistries.MOB_EFFECT, new ResourceLocation("example-mod", "tater"), TATER_EFFECT);
	}
}

Texture

The status effect icon is a 18x18 PNG which will appear in the player's inventory screen. Place your custom icon in:

resources/assets/example-mod/textures/mob_effect/tater.png

Download

Translations

Like any other translation, you can add an entry with ID format "effect.example-mod.<effect-identifier>": "Value" to the language file.

{
  "effect.example-mod.tater": "Tater"
}

Testing

Use the command /effect give @p example-mod:tater to give the player our Tater effect. Use /effect clear @p example-mod:tater to remove the effect.

INFO

To create a potion that uses this effect, please see the Potions guide.