Slimeballs are the quiet enabler of advanced Minecraft. They craft into slime blocks and sticky pistons, the two components behind flying machines, hidden doors, and most compact redstone contraptions, and into leads for moving animals. If you have ever wanted to build serious redstone, you have wanted a slime farm.
The catch is that slimes spawn in two specific, awkward situations, and a farm targets one of them: slime chunks deep underground. Find one, dig out the spawn floors, and you have an endless slimeball supply feeding your redstone projects.
This guide targets Minecraft 26.2 Java Edition. It is a spoke of the farm guides hub, and the slime blocks and sticky pistons it feeds power the builds in the redstone handbook.
What a slime farm produces
- Slimeballs, which craft into slime blocks, sticky pistons, leads, and magma cream for potions.
- The raw material for flying machines and compact redstone, since slime blocks move connected blocks with pistons.
- A steady supply once the spawn floors are cleared and lit correctly.
Where slimes spawn
Slimes have two spawn rules, and this changes your whole approach:
- Slime chunks: in about 1 in 10 chunks, slimes spawn below Y level 40 at any light level, on any valid floor. These chunks are fixed per world seed and are the basis of most slime farms.
- Swamps: slimes also spawn in swamp biomes at night, in a specific light and Y range, on the surface.
A slime-chunk farm is the reliable, all-hours option; a swamp farm is simpler to build but only runs at night. This guide focuses on the slime-chunk method.
Finding a slime chunk by hand is slow. The reliable way is to note that slime chunks are determined by the world seed, so an external slime-chunk finder (fed your seed) tells you exactly which chunks qualify. In-game, you can confirm a chunk by digging out a large flat area below Y 40 and waiting, slimes will eventually appear if it is a slime chunk.
How it works
- Find a slime chunk and confirm it (below Y 40).
- Dig out spawn floors. Hollow large flat layers across the whole chunk, stacked with a few blocks of headroom, so slimes have lots of spawn space.
- Light everything else. Slimes ignore light, but you must light nearby caves so other mobs do not steal the mob cap.
- Funnel and kill. Slimes wander, so water streams or a sloped floor push them to a collection point where you kill them (they split into smaller slimes, so the kill chamber must handle the small ones too).
Building it
- Clear the chunk. Mine out several wide, flat spawn floors within the slime chunk below Y 40, aligned to the chunk borders (understanding chunk borders helps you stay inside the right chunk).
- Light the surroundings. Torch or seal every cave and dark space near the farm so the mob cap is not wasted on zombies and skeletons.
- Water funnels. Add water streams on each spawn floor that carry slimes to a central drop or channel.
- Kill chamber. Route slimes to a chamber where you kill them, remembering big slimes split into medium and small, so the design must funnel all sizes. Hoppers below feed chests.
- AFK spot within range so spawns keep running.
Common mistakes
- Building above Y 40. Slime-chunk slimes only spawn below Y 40. Too high and nothing spawns.
- Not confirming the slime chunk. Digging out the wrong chunk produces zero slimes. Verify first.
- Leaving caves unlit. Other mobs eat the mob cap and starve your slime spawns. Light or wall off everything nearby.
- Kill chamber that only handles big slimes. Slimes split when hit; the funnel and kill area must catch the small ones too, or slimeballs escape.
Rates and optimization
Slime-chunk farms produce a steady, useful trickle rather than a flood, because slimes compete with all other underground spawns for the mob cap. To improve rates:
- Clear and light a wide area so nothing else spawns nearby, giving the mob cap to slimes.
- Dig out more spawn floors to increase valid spawn space within the chunk.
- Consider a mob switch elsewhere in the world to suppress general hostile spawns and hand more of the cap to the farm; see the mob switch guide.
For most players, one slime-chunk farm supplies all the slimeballs their redstone will ever need.
Frequently asked questions
How do I find a slime chunk?
Slime chunks are fixed per world seed (about 1 in 10 chunks). Use a slime-chunk finder with your seed to locate them, or dig out a large flat area below Y 40 and wait to see if slimes spawn.
What Y level do slimes spawn at?
In slime chunks, slimes spawn below Y 40 at any light level. In swamps they spawn on the surface at night in a specific light range instead.
Why is my slime farm not spawning slimes?
The usual causes: the farm is above Y 40, it is not actually in a slime chunk, or nearby caves are stealing the mob cap. Confirm the chunk, dig below Y 40, and light everything around the farm.
Do slimes need darkness to spawn?
No. Slime-chunk slimes spawn at any light level, which is unusual. You still light the surroundings so other mobs do not compete for spawns, but the spawn floors themselves do not need to be dark.
A slime farm unlocks the sticky pistons and slime blocks that serious redstone runs on. With a steady slimeball supply, the flying machines and contraptions in the redstone handbook become buildable, and the farm guides hub covers every other farm your base will want.
