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Getting started with In Control

This guide assumes that you have never written JSON. By the end, you will have made one rule, reloaded it without restarting Minecraft, and tested that it works.

These instructions are for Minecraft 1.20.1 and newer. Individual settings can differ between versions, so check the version notes in the technical reference when copying an advanced rule.

First: choose the right file​

In Control uses several files because they react to different things. For a first configuration, this is the important distinction:

I want to…Start with
Stop or limit a mob that already spawnsspawn.json
Make a mob spawn more oftenspawner.json
Add a mob somewhere it does not normally spawnspawner.json
Change a spawned mob's health, damage, speed, equipment, or AIspawn.json with "when": "finalize"
Change drops or experienceloot.json or experience.json
React when a mob dies or a block breaksevents.json
Prevent breaking, placing, or clicking a blockbreakevents.json, placeevents.json, leftclicks.json, or rightclicks.json
Give a reusable name to a time or world conditionphases.json
Give a name to a regionareas.json
The most important distinction

spawn.json checks spawn attempts that are already happening. It does not create more spawn attempts.

spawner.json creates additional spawn attempts. Those mobs can still be checked by spawn.json.

Vanilla or another mod tries to spawn a mob
                    ↓
             spawn.json checks it

spawner.json creates an extra spawn attempt
                    ↓
             spawn.json may check it too

Your first rule​

We will prevent creepers from entering the world. Using onjoin makes this example easy to test with a spawn egg.

  1. Open the config/incontrol directory of the Minecraft instance or server.
  2. Create a plain-text file named spawn.json if it does not already exist.
  3. Copy the entire example below, including the square brackets.
spawn.json
[
  {
    "mob": "minecraft:creeper",
    "when": "onjoin",
    "result": "deny"
  }
]
  1. Save the file.
  2. In Minecraft, run /incontrol reload.
  3. Try to use a creeper spawn egg.

Expected result: the creeper does not appear. To undo the test, replace the file contents with [], save it, and run /incontrol reload again.

What the rule says​

  • [ and ] contain the complete list of rules in this file.
  • { and } contain one rule.
  • "mob": "minecraft:creeper" is a condition: this rule only matches creepers.
  • "when": "onjoin" checks an entity as it enters the world. This includes spawn eggs.
  • "result": "deny" is the action: prevent the matching entity from entering the world.

JSON survival guide​

You only need a few JSON rules to begin using In Control.

Text needs double quotes​

{ "mob": "minecraft:zombie" }

Do not use single quotes. Numbers and true or false do not use quotes:

{
  "maxcount": 20,
  "hostile": true
}

Separate settings with commas​

Every setting is followed by a comma except the last setting in the same object:

{
  "mob": "minecraft:zombie",
  "result": "deny"
}

Square brackets mean a list​

A file contains a list of rules:

[
  { "mob": "minecraft:creeper", "result": "deny" },
  { "mob": "minecraft:phantom", "result": "deny" }
]

Some settings also accept a list. This condition matches either a creeper or a phantom:

{ "mob": ["minecraft:creeper", "minecraft:phantom"] }

Conditions in one rule are combined​

This rule matches only zombies that are both in the Overworld and above height 100:

{
  "mob": "minecraft:zombie",
  "dimension": "minecraft:overworld",
  "minheight": 100,
  "result": "deny"
}

JSON does not support comments​

Do not put // explanation or # explanation in a rule file. Explanations shown next to examples belong in the documentation, not in the copied JSON.

Use full Minecraft identifiers​

Use identifiers such as minecraft:zombie, not just zombie. Modded identifiers use the mod id, for example examplemod:scary_mob.

A safe editing routine​

Use this loop whenever you change a configuration:

  1. Keep a backup of the last working file.
  2. Change one small thing.
  3. Paste the file into the Control Validator.
  4. Save it in config/incontrol.
  5. Run /incontrol reload.
  6. Read any red In Control error message. The log contains more detail.
  7. Test the exact situation the rule is meant to affect.

The validator catches many common mistakes, but it does not yet cover every rule file or every version-specific setting. A successful validation is helpful, not a guarantee that the rule expresses what you intended.