How to build an XP farm from a spawner in Minecraft

A dungeon spawner makes up to 4 mobs every 10 to 40 seconds while you stand near it. This farm brings them all to one spot where you kill them with your sword and collect their drops. We built it around a spawner on a Java Edition 26.3 server and checked that every zombie placed in the room reaches the hopper.

Orientation used below: the water flows from the west wall to the east wall, where the trench and the drop shaft are. Turn the plan to fit your dungeon, it works in any direction.

Dungeons are small Cobblestone and Mossy Cobblestone rooms underground with a Monster Spawner in the middle. Half of them spawn zombies, a quarter skeletons, a quarter spiders. Use a zombie or skeleton one: spiders do not fit this build.

While you work, place a Torch next to the spawner. In the Overworld a monster spawner only spawns mobs where the block light is 0, so one torch stops it.

1. Dig the room out to 9 by 9 blocks inside, with the spawner in the center, sitting on the floor, and 3 blocks of air above the floor (layers 8 to 11 of the plan). Mobs spawn up to 4 blocks away from the spawner, so this covers the whole spawn area.
2. Build a wall 2 blocks high across the room, through the spawner, from the west wall, stopping 1 block short of the east wall, where the trench goes. Mobs cannot spawn on top of it, and each half of the room now gets its own clean flow of water.

1. Along the east wall, dig the floor 1 block deeper over the whole 9 blocks: that is the trench (layer 8).
2. In the middle of the trench, dig the floor out completely: this is the top of the drop shaft.
3. Place an Oak Sign on the east wall, inside that middle block (layer 8). Water cannot flow into a sign, but mobs fall through it. Use a wall sign: a standing sign over the hole has nothing to stand on and breaks.
4. Pour one Water Bucket at each end of the trench. The water flows toward the sign and stops against it.

Pour a Water Bucket on every floor block along the west wall, 8 in total (layer 9). Water flows 7 blocks, so it covers the room up to the edge of the trench and pushes every mob into it. The trench water then carries them into the sign block, and they drop.

1. Dig the shaft straight down 5 blocks under the sign, 1 by 1, walled on all sides (layers 3 to 7).
2. At the bottom, place a Hopper pointing into a Chest next to it (layer 2). The mobs land on the hopper, which picks up their drops.
3. On the side where you will stand, put a Stone Brick Slab in the top half of the block at the mobs' feet (layer 3), and a full block under it. Leave the 1 by 2 space next to the slab open for you, with a block above your head.

The fall costs the mobs 2 of their 20 health. Babies cannot squeeze through the half block gap, and a mob only reaches you if its attack box touches you: standing 2 blocks from the shaft, you are out of reach.

1. Remove every torch from the room, then go to the kill spot. You must stay within 16 blocks of the spawner for it to work: the kill spot is about 9 blocks away.
2. Hit the mobs' feet through the gap. A Diamond Sword with Smite V deals 7 + 12.5 = 19.5 damage to undead mobs, enough to kill an 18 health zombie or skeleton in one hit; with Sharpness V (10 damage) it takes two. Mobs wearing armor can take one more. Our best sword enchantments guide covers the rest of the sword.
3. Kill them before they pile up: the spawner stops while 6 of its mobs are within 4 blocks of it.

An adult zombie gives 5 experience points, plus 1 to 3 for each piece of gear it wears or holds, and a baby zombie 12. Going from level 0 to 30 takes 1,395 points, about 280 adult zombies: that is what the level 30 enchanting setup asks for.

All spawner rules and numbers here come from Java Edition 26.3, where we tested the build. Spawners and mob spawning follow different rules on Bedrock Edition, so the layout has not been checked there.