How to Build a Mob Farm in Minecraft (Java and Bedrock)

A mob farm in Minecraft is a dark floor where monsters spawn, with water that carries them to a kill chamber and hoppers that collect the loot. In Java, monsters only spawn where block light is 0, at least 24 blocks from every player and within 128 blocks of one. Build it high in the sky or above an ocean, so caves don’t steal your spawns. Checked against Java 26.3, with Bedrock and server notes further down.

How does a mob farm work?

Every farm leans on the spawning rules from the Minecraft Wiki. Most monsters spawn in groups of up to four, on a solid block, in the dark. Glass, leaves, trapdoors, scaffolding and water don’t count as floor. The 26.3 game files confirm the light rule: block light must be 0, and the light level is checked against a random number from 0 to 7.

• Distance. Nothing spawns within 24 blocks of a player. Further than 128 blocks away, monsters despawn at once.
• Walking. With no player within 32 blocks, most mobs stop wandering after about five seconds. A farm where mobs must walk into a hole needs you close by.
• The mob cap. In Java each player has a cap of 70 monsters, and every monster in the chunks around you counts. A zombie in a cave below you takes a spot your farm could have used.

That’s why location matters. According to the wiki, surface farms mostly work by day, underground farms compete with every unlit cave, and sky farms spawn best day and night. The catch: you have to stay at the height of the farm. Above an ocean, only caves under the seabed and drowned are left to compete.

Spawning platform or spawner?

A spawner farm is built around a monster spawner, usually one in a dungeon. It tries to spawn four mobs, then waits 10 to 40 seconds, and it skips a round once six of its mobs are nearby. It’s easy and it’s the classic for levels, because you land the final hit: see how to build an XP farm. For lots of bones, arrows, string and gunpowder at once, you need a platform.

Build a simple mob farm in Minecraft step by step

This is how to build a mob farm in Minecraft that runs day and night. It’s a dark room mob farm with water channels, based on the wiki’s compact canal design.

1. Pick the spot. High above an ocean is best. On land, light up every cave around the farm.
2. Lay a floor of about 20 by 20 blocks with a hole in the middle. Use solid blocks, not glass or bottom slabs.
3. Dig water channels to the hole, exactly 8 blocks long, with the water sources at the far ends. The water then stops right at the edge of the hole. The wiki’s design uses eight water sources.
4. Line the channels and the hole with open trapdoors. Mobs see an open trapdoor as solid floor, walk onto it and drop into the water.
5. Put a roof two blocks above the floor. That keeps endermen out. Don’t place a single torch inside.
6. Deal with spiders. They climb walls and can clog the hole. The wiki shows a carpet pattern on the floor that stops them spawning.
7. Build the drop and collect the loot. Below the hole goes the kill chamber, with hoppers into chests. A hopper costs five iron ingots and a chest, so an iron farm comes in handy.
8. Pick your AFK spot. Stay more than 24 blocks from the floor, but within 32 blocks of all of it, so the mobs keep walking. With a 20 by 20 floor, about 25 blocks straight below the hole works.

Want more output? The wiki’s spawning tower flushes each platform with water from dispensers, driven by observers and a clock. Then mobs don’t have to walk, so distance matters less.

The kill chamber: which mob grinder works best?

• Fall damage. A drop of 24 blocks kills most common monsters; zombies, skeletons and creepers die from 23.5. Witches need a longer drop, and spiders need a shaft of 2 by 2. Mobs with Feather Falling boots can survive, so magma blocks at the bottom help.
• Campfires. Most monsters die on one in under 10 seconds, and the loot survives. A hopper under the campfire pulls the items through. A soul campfire kills twice as fast and gives off less light. Witches heal themselves, so finish those by hand.
• Magma blocks. One heart of damage per second, so an unarmored skeleton lasts about 10 seconds. Hopper minecarts underneath collect the loot. Most Nether mobs are immune.
• A lava blade. Lava held up by a sign at head height, with the items falling into hoppers below. Baby zombies can slip underneath.

An automatic grinder gives no experience: mobs only drop it when you or your tamed wolf kill them. For levels, build a spawner farm next to it.

What is different in Bedrock?

• A smaller spawn ring. At simulation distance 4, mobs spawn 24 to 44 blocks from you. From 6 and up it’s 24 to 128 blocks, but only about 96 blocks sideways.
• Tighter caps. Bedrock counts mobs per area of 9 by 9 chunks. In the Overworld that’s 8 monsters on the surface and 16 in caves, with a global cap of 200. Kill fast, or the farm stalls.
• Stricter floors. Mobs need a full, solid top surface and can’t spawn on see-through blocks. Monsters also need sky light below 7 and block light 0.
• Other designs. A Bedrock trick is water on scaffolding. Mobs spawn with their feet in the scaffolding and their heads in flowing water, which carries them off at once. In Java nothing spawns on scaffolding.

Mob farms on a server: lag and the mob cap

• The mob cap on a server. Paper’s default bukkit.yml sets spawn-limits: monsters: 70, and per-player-mob-spawns: true in config/paper-world-defaults.yml counts that limit per player. Monsters within 128 blocks of you fill your cap, also those in a friend’s caves.
• Two AFK players don’t double it. The global cap grows with the number of loaded chunks, and chunks near several players count once.
• Range and activity. mob-spawn-range in spigot.yml is 8 chunks. Monsters further than 32 blocks from a player tick less often there (entity-activation-range), so keep the platform close.
• Simulation distance. Entities only move within simulation-distance, 10 chunks by default in server.properties. Set it very low and the farm’s area shrinks too.
• Game rules. Keep spawn_mobs, spawn_monsters and mob_drops on true, and the server off Peaceful. A spawner also needs spawner_blocks_work. Paper doesn’t count spawner mobs toward the limit (count-all-mobs-for-spawning: false).
• Cramming. More than 24 mobs packed into one space take damage (max_entity_cramming). On Paper, players don’t take that damage by default.
• Lag. Mob AI costs server time, so kill quickly and send items straight into chests. Find lag with Spark shows which farm is the heaviest. By default the server doesn’t kick idle players (player-idle-timeout=0).