Tutorials/Iron golem farming

Iron golem farming uses village mechanics to produce iron, as well as byproducts such as poppies and string. Usually, an iron golem farm is a player-constructed village in which golems are spawned and then either killed immediately or moved to a holding cell outside the village boundary for later killing. Iron golem farming is preferable to other methods of iron farming from zombies and skeletons due to a much higher chance of iron dropping and therefore much higher quantities of iron.

Java Edition
$$, a villager can attempt to spawn an iron golem while not having a golem alive within the box of the range 16 blocks around the villager and more than 30 seconds has passed.

An iron golem needs an available volume in which to spawn. There must be at least 3 transparent blocks above the spawning surface, which must be solid and flat (but not a bottom slab).

Cat cap
Villages spawn cats also, one cat for every four valid beds and one villager. The cat population is capped at 10 cats per village. Golems cannot spawn once the cat cap is reached. Because your farm starts producing cats before it's ready to produce iron golems, you must be sure that your farm kills enough cats to keep the population under 10. A few cats hanging around doesn't present a problem, but you should occasionally patrol the area for cats hiding and other places where they may go or get stuck, and kill them. If the cap is reached, cats must be killed near enough to the villagers (preferably within 16 blocks) so that the villagers are aware that the cat has died, or they don't resume causing new iron golems to spawn. Villagers won't notice the death of cats that have wandered off too far or fallen off a cliff (cats take no fall damage) and are still living below. Killing cats too far away has no effect on the cat cap.

Spawning requirements
Villages attempt to spawn iron golems around the village center when the following requirements are met:
 * The village contains at least 20 beds.
 * The village contains at least 10 villagers (make sure that a villager is not a nitwit or a baby).
 * 100% of villagers are linked to a bed.
 * At least 75% of villagers have worked at their workstations within the past day.
 * A player is within 80 blocks of the village horizontally and within 44 blocks vertically.
 * There is less than one naturally generated or spawned (i.e. not player-created) iron golem for every 10 villagers in the village. The ratio of iron golems to villagers is rounded down to the nearest whole number, so to spawn a second iron golem while the first is still alive requires 20 villagers, to spawn a third golem requires 30 villagers, and so on.

There is a 1/700 chance of an iron golem spawn attempt during each game tick when these conditions are met. This averages to one spawn attempt every 35 seconds.

On each spawn attempt, the game checks 10 random X, Y, Z coordinates in the 16×6×16 volume around the village center. The spawn attempt succeeds if a chosen coordinate meets the following conditions:
 * There is a solid block underneath.
 * The 2×4×2 volume extending -1 X (west), +3 Y (upward), and -1 Z (north) from the chosen coordinate does not contain any solid blocks.

If these conditions are met but there is a partial or transparent block at the chosen coordinate, then the iron golem may appear to spawn on top of the partial or transparent block. This gives the appearance that iron golems can spawn on top of normally non-spawnble blocks like bottom slabs, carpets, and glass.

Village center
A village center is the northwest bottom corner of a point-of-interest (POI) block, which can be a bed pillow, bell, or workstation. The village center always begins as the pillow of the first bed linked to a villager. It can shift when a villager links to a new POI or unlinks from a POI after three failed attempts to pathfind to it, or after removal of either the villager or the POI from the village. The game attempts to make the village center correspond roughly to the geometric center of all linked POI in a village, but there is randomness involved and shifts can seem erratic.

Controlling the village center is often the most difficult part of designing, building, and maintaining an iron golem farm. The center is important because it determines where structures must be built to spawn, contain, and transport the iron golems. Iron golems can spawn in a 16×6×16 volume around the village center point; that is, 8 blocks in all horizontal directions from northwest bottom corner of the POI block, and 2 blocks above the top and 3 blocks below the bottom of the POI block. To protect against center shifting and also capture all available iron golem spawn attempts, farm designs commonly cluster beds at the center of the farm and have the spawn platform(s) extend 8 blocks out from the furthest bed pillows in each direction.

It is best to avoid using bells in iron golem farms because villagers try to pathfind to bells at gathering time, fail, and then unlink from the bell, causing the village center to shift. A bell does not define a village center. The game also does not indicate which villager's bed defines the village center.

Farm designs that do not allow villagers to access their beds may experience center-shifting and possibly lower spawning rates unless they prevent villagers from unlinking from the beds at night. To prevent a villager from unlinking, you can either place water on its feet, or prevent it from attempting to pathfind by surrounding it with blocks.

Maximizing rates
The rate of iron ingot production in an iron golem farm is determined by three factors: the number of spawnable blocks, the number of villagers, and the average lifetime of each iron golem. The most efficient farms achieve rates around 400 ingots/hour.

The maximum number of spawnable blocks in a farm is 512. This is achieved by two minimum 16×16 solid block platforms centered horizontally at the village center, with one platform four blocks under the village center, and the other platform a block above the village center. In farms designed for maximum rates, the beds are usually arranged tightly around the horizontal center on the Y-level just below the upper spawn platform. This allows iron golems to be transported underneath the beds and ensures that the Y-level of the center does not shift. With 512 spawnable blocks, 98.3% of spawn attempts can succeed.

Increasing the number of villagers allows additional spawn attempts to succeed during the time it takes to transport and kill existing iron golems. In a farm using water to transport iron golems and lava blades to kill them, increasing the population from 10 to 20 increases rates by about 33%, and increasing the population from 20 to 30 increases rates by about 5%.

The average lifetime of iron golems depends on transport time and kill time. Most farms use water to transport and lava blades (lava suspended on transparent blocks) to kill. It is also possible to use rail systems or sand pushers to transport iron golems. Rail systems are likely slower than water, and sand pushers are difficult to build and maintain. Other kill methods such as magma blocks, skeleton arrows, and trident killers are slower than lava. However, trident killers can kill faster than lava if the tridents are enchanted with Impaling V and the iron golems are kept in contact with water. The kill method does not affect the average number of ingots dropped by each iron golem.

Java Edition videos

 * 1.16.2 farm
 * 1.16 farm
 * 1.16 farm
 * 1.16 farm

Bedrock Edition videos

 * 1.16 iron farm mechanics


 * 2-platform 1.16 trading hall iron farm


 * 2-platform 1.16 farm with villagers in tileable workstation pods