MobRules

MobRules is a lightweight mod for Minecraft 1.21.1 & 26.2 that provides comprehensive and granular control over mob spawning through three distinct categories:

• Hostile Mobs: All aggressive creatures including monsters, undead, and other threats
• Farm Animals: Domestic and passive land animals typically used for resources or companionship
• Aquatic Animals: All water-dwelling creatures from fish to amphibians

Each category offers three levels of control:

• Allow All (allow_all): Normal vanilla spawning behavior
• Block All (block_all): Completely prevent spawning for the entire category
• Selective Control (allowlist): Use customizable JSON allowlists to specify exactly which mobs can spawn

Categories are resolved from each mob's vanilla spawn category, so modded mobs are covered automatically. Every mob belongs to exactly one category, so a spawn is only ever evaluated once.

Advanced Configuration

When using "partial" mode, MobRules generates JSON allowlist files in your config/mobrules/ directory:

• hostile_mobs_allowlist.json - Controls which hostile mobs can spawn
• farm_animals_allowlist.json - Controls which farm animals can spawn
• aquatic_animals_allowlist.json - Controls which aquatic animals can spawn

These files are automatically created with sensible defaults and can be edited to include only the specific mob IDs you want to allow. For example:

[
  "minecraft:zombie",
  "minecraft:skeleton",
  "minecraft:creeper"
]

Reclassifying mobs

To move a mob into a different category (for example, treating an amphibian as aquatic rather than farm), edit config/mobrules/category_overrides.json:

{
  "minecraft:frog": "aquatic"
}

Valid categories are hostile, farm, and aquatic.

In-game commands

All commands require permission level 2 (operator):

• /mobrules status — show the current control mode and allowlist size for each category
• /mobrules reload — reload the allowlist and override files from disk without restarting
• /mobrules allow <category> <mobId> — add a mob to a category's allowlist
• /mobrules disallow <category> <mobId> — remove a mob from a category's allowlist

Why MobRules Exists

Every Minecraft player has encountered situations where default spawning mechanics don't align with their goals:

• Creative builders who want inspiration from a living world without combat interruptions
• Server administrators managing performance with selective mob populations or creating themed areas
• Modpack creators needing precise control over which creatures populate their custom worlds
• Accessibility-focused players who want to reduce specific stressors while maintaining gameplay
• Role-playing servers requiring specific atmospheric conditions with custom creature populations
• Adventure map makers who need exact control over which mobs appear in different areas

MobRules bridges the gap between Minecraft's default spawning and the diverse needs of its community, offering everything from simple on/off switches to precise per-mob control through easy-to-edit configuration files.