Farms Builds

Farmland, water and light

Farmland stays wet when water is up to four blocks away, diagonals included, on the same level or one block higher. Flowing water counts as much as a source block, so a single block of water in the middle of a 9x9 field keeps all of it wet. Crops grow faster on wet farmland and need a light level of 9 or more to grow at all, which is why torches keep a field growing through the night.

Bone meal moves a crop 2 to 5 stages ahead. A crop breaks when a piston pushes it or when its farmland turns back into dirt, and farmland does that when players or mobs keep landing on it. That is why the basic wheat farm has a fence around it.

Farmer villagers

An unemployed villager can take a free composter as its job site and become a farmer. Farmers harvest wheat, carrots, potatoes and beetroot once they are fully grown, use bone meal on younger crops when they can and plant seeds again. In the villager crop farm hopper minecarts under the field collect the drops, since a minecart with a hopper picks up items through one layer of solid blocks.

Composters

Cake and pumpkin pie always raise the compost level. Bread, baked potatoes and hay bales do so 85% of the time, wheat seeds 30%. A hopper above a composter fills it and a hopper below takes the bone meal out, which is all the composting station needs. A composter beside the automatic crop farm turns its spare seeds into bone meal.

Plants that grow back

Sugar cane, cactus, bamboo and kelp need no farmland and no replanting. Cut them above the bottom block and they grow again from it, so their farms only have to break and collect.

Sugar cane

Grows on dirt, grass, sand, moss or mud right next to water, up to three blocks tall and even in complete darkness. Bone meal does nothing to it in Java. Zero-tick farms stopped working in Java in 1.16 and still work in Bedrock, so the auto sugar cane farm harvests with observers and pistons.

Cactus

Can only stand on sand, red sand or another cactus, and breaks as soon as a solid block or lava is beside it. The automatic cactus farm puts a block next to the space each cactus grows into, so the new piece breaks off by itself. Cactus destroys dropped items that touch it, so the drops need a clear way down.

Bamboo

Each random tick gives it a 1 in 3 chance to grow. In Java that is a block about every 3.4 minutes, where sugar cane takes about 18, and it keeps going to 12 to 16 blocks as long as the top has light level 9. A piston that pushes bamboo turns it into an item, which is how the auto bamboo farm collects it.

Kelp

Grows without light or open sky until the top of the plant reaches age 25, and bone meal adds a block per use. A dried kelp block smelts 20 items, so the auto kelp farm is a fuel farm as much as a food farm.

Melons and pumpkins

The stems grow on farmland and put their fruit on a free dirt, mud or moss block next to them, at light level 9 or more. A piston breaks a melon or pumpkin into drops, so an observer that sees the fruit appear can fire one, which is what the melon and pumpkin farm does.

Trees

Birch grows quickly to the most even height, which makes it the usual pick for an automatic farm. Oak and dark oak leaves drop apples, but an oak sapling can grow into a large oak that is slow to clear, and dark oak and pale oak only grow from four saplings in a 2x2 square. The automatic tree farm bone meals its saplings from dispensers and spots the new log with an observer.

How monsters spawn

In the Overworld most monsters spawn only where the block light is 0 and the sky light is 7 or less. In the Nether the block light has to be 7 or less, and in the End it has to be 0. Most don't spawn within 24 blocks of a player, and in Java they disappear at once when no player is within 128 blocks, so the spawning floors of a mob farm belong between those two distances from where you wait, with as few other dark spaces around as you can manage.

A monster spawner works differently. It only runs while a player is within 16 blocks, tries to place 4 mobs in a 9x3x9 space around itself and then waits 10 to 40 seconds. The mob spawner XP farm and the spider farm are both built around one. Spiders climb any solid wall but never along the underside of a block, so a ledge sticking out at the top of the wall keeps them in.

Mobs only drop XP when a player or a tamed wolf hit them in the 5 seconds before they died, so a farm that kills with fall damage alone gives no XP. Most mobs take 1 damage for every block they fall beyond 3, and zombies and skeletons have 20 health, so a 22 block drop leaves them one sword hit from death.

Creepers

Trapdoors under a 2 block high ceiling leave 1 13/16 blocks of room, enough for a creeper and too little for a zombie or skeleton. Spiders still fit unless carpets with two blocks between them break up the floor, and in Bedrock the trick doesn't work. Creepers run from cats within 6 blocks, which is how the creeper farm drives them into its water.

Slimes

About one chunk in ten is a slime chunk, and there slimes spawn anywhere below Y 40 at any light level. In swamps they spawn between Y 51 and 69 at light level 7 or less. A slime goes after a player within 16 blocks, or an iron golem if no player is there, which is how the slime farm lures them onto its magma blocks.

Drowned

They spawn more often in rivers than in oceans, and in Java river drowned also spawn in daytime where the water is deep enough to be dark. Only drowned that spawn with a trident can drop one: 6.25% do, and in Java a player kill drops it 8.5% of the time, plus 1% per level of Looting. Zombies that turn into drowned never carry one. The drowned farm also gives copper ingots when a player gets the kill.

Endermen

They need three free blocks above the spawning block, and in the End a block light of 0. The enderman XP farm is built in the End at least 128 blocks from anywhere else they could spawn, so they can only appear on its platform. Endermen attack any endermite they can see within 64 blocks, and a named endermite never despawns, which makes it a lure that keeps working.

Witches

In Java only witches spawn in the small area around a swamp hut, as long as the whole hut stands in a swamp biome, and one hut has room for up to three spawning platforms. That is what lets the witch farm sort itself.

Guardians

They spawn only in ocean monuments, so the guardian farm is built into one after draining it.

Nether farms

Blazes

Blazes spawn at light level 11 or less, in a fortress or from one of its blaze spawners, and a fortress has at most two of those. Blaze rods only drop when a player or a tamed wolf gets the kill. Water from a bucket vanishes in the Nether, so the blaze farm has to move blazes some other way.

Zombified piglins

Fire, lava and magma blocks can't hurt them. In the Nether only they, ghasts and magma cubes can spawn on magma blocks, so a magma floor narrows the spawns down to those three. In Java they go after turtle eggs in a 47x7x47 area around them, and the eggs only hatch on sand. The nether gold farm uses the eggs to lead them over a drop.

Wither skeletons

They spawn in fortresses at light level 7 or less, in groups of five in Java. Wither roses give blazes, zombified piglins and other mobs that touch them the Wither effect, but wither skeletons are immune and can even spawn inside them, which is why the wither skeleton farm puts wither roses on its platform. A player kill drops a skull 2.5% of the time, 5.5% with Looting III.

Villagers, golems and raids

In Java villagers summon an iron golem when at least three of them within 10 blocks panic together, usually at the sight of a zombie, or when five gossip. Each of them must have slept in the last 20 minutes and must not have detected a golem or been near a summoning in the last 30 seconds. So every villager in the iron golem farm needs a bed, and one group makes a golem every 30 seconds at most. A golem drops 3 to 5 iron ingots.

A villager is willing to breed with 3 bread, 12 carrots, 12 potatoes or 12 beetroot, and every baby needs a free bed with two empty blocks above it. In Java a baby is 0.98 blocks tall and an adult 1.95, so a gap one block high lets the babies out of the villager breeder and keeps the parents in. Send the new villagers on to the trading hall.

The raid farm needs only one villager, since in Java any bed, job site block or bell that a villager has claimed makes a village. Raids never start in the Nether.

Cobblestone, honey and animals

A cobblestone generator depends on which lava meets the water. Flowing lava that touches water becomes cobblestone and lava flowing down onto water makes stone, but water that reaches the lava source turns it into obsidian and ends the generator. Keep the flowing water away from the lava source block.

Every pollinated bee that leaves a hive or nest after working raises its honey level by one, up to 5. A comparator reads that level, and a dispenser facing a full nest fills glass bottles with honey or uses shears to collect honeycomb, which is how the automatic honey farm runs on its own. Move a nest with a Silk Touch tool so the bees stay inside and calm.

In the animal pen, cows and sheep breed with wheat, pigs with carrots, potatoes or beetroot and chickens with seeds. Hay bales are for horses and llamas: they heal both, and llamas breed with them.