Mob Spawn Control

Mob Spawn Control is a lightweight, Server-Side configuration-driven mod for Minecraft 1.21.x, 26.1.x, and 26.2.x. It gives you complete control over mob spawning with per-rule filters, category caps, loot/XP scaling, attribute multipliers, and mob replacement no coding required, just edit the JSON config and reload.

Supported Versions

Purpose & Function

The core mission of this project is to give server operators and modpack makers fine-grained spawn control with zero performance overhead.

• Rule-Based Filtering: Define spawn rules by dimension, biome, block, spawn type, light level, height, time, weather, and player proximity.
• Per-Rule Overrides: Each rule can set custom spawn rates, category caps, attribute multipliers, XP/loot scaling, and replacement mobs.
• Hot Reload: Change your config file at any time and run /spawncontrol reload no server restart needed.
• Full Command Suite: In-game commands to inspect active rules, ban/unban dimensions, biomes, spawn types, and blocks, tweak rates, caps, height/light limits, attributes, weather conditions, and replacement targets.
• Lightweight & Efficient: Minimal mixins, early-out checks, proximity search optimized to skip when unused no tick overhead when rules don't match.

Key Features

Enhance your server setup! Check out my other server-side mods over at : Fabric Server Essentials

Configuration

The mod reads config/viper_spawn_control.json. Here's a quick example:

{
  "spawnRules": [
    {
      "id": "no_creepers_underground",
      "enabled": true,
      "mob": "minecraft:creeper",
      "spawnTypes": ["NATURAL"],
      "maxHeight": 0,
      "action": "DENY"
    },
    {
      "id": "buffed_zombies_night",
      "enabled": true,
      "mob": "minecraft:zombie",
      "spawnTypes": ["NATURAL"],
      "time": { "minTime": 13000, "maxTime": 24000 },
      "action": "ALLOW",
      "attributeMultipliers": {
        "maxHealth": 2.0,
        "movementSpeed": 1.5,
        "attackDamage": 2.0
      },
      "lootMultiplier": 2.0,
      "experienceMultiplier": 3.0
    },
    {
      "id": "replace_spiders_with_cavespiders",
      "enabled": true,
      "mob": "minecraft:spider",
      "spawnTypes": ["NATURAL"],
      "action": "REPLACE",
      "replaceWith": "minecraft:cave_spider",
      "replaceDepth": 1
    }
  ],
  "biomeSpawnAdditions": [
    {
      "entityType": "minecraft:polar_bear",
      "biomeId": "minecraft:plains",
      "weight": 5,
      "minGroupSize": 1,
      "maxGroupSize": 2
    }
  ],
  "categoryCaps": {
    "MONSTER": 80,
    "CREATURE": 15,
    "AMBIENT": 15,
    "WATER_CREATURE": 10,
    "WATER_AMBIENT": 25,
    "AXOLOTLS": 5,
    "UNDERGROUND_WATER_CREATURE": 10
  }
}

Commands

/spawncontrol reload                     Reload config from disk
/spawncontrol info [mob]                List rules or rule details for a mob
/spawncontrol ban <dimension|biome|block|spawntype> <value>   Ban/drop specific value from rules
/spawncontrol unban <dimension|biome|block|spawntype>          Unban a previously banned value
/spawncontrol rate <mob> <rate>         Set random spawn rate for a mob
/spawncontrol cap <category> <cap>      Override mob cap for a spawn category
/spawncontrol spawntype <type>           Show rules matching a spawn type
/spawncontrol height <mob> <min> <max>  Set height limits for a mob
/spawncontrol light <mob> <min> <max>   Set light level range for a mob
/spawncontrol attributes <mob> <health|speed|damage> <mult>   Set attribute multiplier
/spawncontrol weather <mob> <clear|rain|thunder>               Toggle weather condition
/spawncontrol replace <mob> <replacement> [depth]              Set mob replacement target

Note: When using the /spawncontrol ban command, ensure the value is enclosed in quotes (e.g., /spawncontrol ban "minecraft:sheep" instead of without quotes), otherwise the command will fail to parse correctly.

Built for server operators who demand surgical precision over vanilla spawning. Define it once, reload on the fly, and never fight spawn rates again.