How to Make an Iron Farm

Guide Java Bedrock

Quick answer: Trap 3 villagers with beds and workstations, place a zombie where they can see it but not reach it, and the panicking villagers summon iron golems. Spawn platforms funnel the golems into lava or a kill chamber with hoppers, producing iron automatically. Java and Bedrock designs differ, so follow one for your edition.

What you need

3 villagers + 3 beds + 3 workstations
1 name-tagged zombie
Building blocks, water, lava, hoppers, chests
Name tag (anvil)

Step by step

Understand the mechanic. In Java, villagers who panic at the sight of a hostile mob (or gossip in groups of 5) summon iron golems around themselves - as long as they have slept and worked recently. The golem spawns on solid blocks near the villagers.
Build the villager pod. Place 3 beds, 3 villagers and 3 workstations (fletching tables are cheap) in a small sealed room. They must be able to sleep at night and work by day - that's what keeps golems spawning.
Add the scare. Put a zombie (name-tagged so it never despawns) one block of sight away from the villagers, behind trapdoors or a piston system that periodically breaks line of sight so they can sleep. No direct path to them.
Build spawn platforms and a kill chamber. A solid platform around the pod with water streams pushes spawned golems into a lava blade or drop chute; hoppers below feed chests. Golems drop 3-5 iron and a poppy.
Keep it isolated. Build the farm at least 64 blocks from any other villager or village, and spawn-proof the surroundings so golems only spawn on your platform. Decorate with the poppies as a bonus.

Java vs Bedrock

Java uses the panic/gossip mechanic described here. Bedrock iron farms are different: they need 10 villagers, 20 beds, and 75% of villagers working, with golems spawning around the village center - follow a Bedrock-specific design for that edition.

Versions: Villager-summoned golem farming has existed since 1.8. The 1.16 update made golems spawn only after villagers sleep and work, killing the old 'door village' farms and standardizing the modern 3-villager panic design.

Frequently asked questions

Why did my iron farm stop working?

The villagers can't sleep (zombie visible all night), can't reach workstations, or the zombie despawned or died. Name-tag the zombie and use a piston/trapdoor timer to break line of sight periodically.

How much iron does it make?

A simple 3-villager Java farm produces iron steadily, and stacking more modules scales that up. Enough for beacons, anvils and hoppers.

Can I build it in the spawn chunks?

Yes, and it will even run while you're away in Java. But the classic spot is near your base with an AFK platform above.