Slime Chunk Finder

The Rules Behind Slime Chunks

A few quick facts that make the difference between "a farm that works" and "a farm that's somehow empty".

• Which chunksRoughly 10% of chunks in every seed are Slime Chunks. They're set when the world is created, and the finder shows you exactly which ones in your seed so you can pick the best spot.
• Spawn depthSlimes only spawn below Y 40 in Slime Chunks. They ignore light level (unlike most hostile mobs), so your farm doesn't need to stay dark.
• SwampsOutside Slime Chunks, slimes also spawn in swamp biomes between roughly Y 50 and Y 70 at low light. Spawn rates are tied to the moon phase — full moon gives the highest chance, new moon blocks them entirely. It's slower than a chunk farm but works if you can't travel to a confirmed chunk.
• Mangrove swampsMangrove swamps spawn slimes the same way as regular swamps, with the same moon-phase modifiers. That's handy if one happens to sit near your base — you can build a small surface farm without needing to travel to a Slime Chunk.
• Despawn ruleSlimes will despawn if you're more than around 128 blocks away from them, so where you AFK in your farm matters. Too close and they don't get a chance to spawn around the chunk; too far and they vanish before reaching the kill point.

Building a Simple Slime Farm

If you've found a nearby Slime Chunk, you're about twenty minutes away from never crafting slimeballs again. A basic farm is just an open room at the right Y level in the right chunk — no redstone tricks needed for a starter version.

1. Get to Y 30 inside the Slime Chunk. A chunk is a 16×16 column of the world running from bedrock to the build limit, and the finder pin marks the corner of the slime-spawning chunk. In Java Edition you can press F3 to bring up the debug screen and F3+G to overlay chunk borders so you can see the boundaries clearly. Mine down to roughly Y 30 — slimes spawn anywhere below Y 40 but Y 30 gives you a comfortable ceiling for the farm.
2. Hollow out a 16×16×4 room aligned to the chunk borders. Slimes can spawn in any air block within the Slime Chunk that's below Y 40, so the bigger the cleared volume the higher the spawn rate. A single 16×16×4 floor is the minimum useful size; a multi-floor stack of those rooms (each 4 blocks tall, separated by a 2-block ceiling) is the standard high-rate design once you scale up.
3. Light up every dark cave within 128 blocks of the farm. The game limits how many hostile mobs can exist around a player at once (the "mob cap") — and that cap is shared across every dark spawnable space inside your simulation radius. A single unlit cavern can fill up with regular zombies and skeletons that count against the cap, leaving no "room" for slimes to spawn in your farm. Torch every nearby cave aggressively before testing the rates.
4. Build a kill mechanism that handles all three slime sizes. Slimes spawn in three sizes — big (4 blocks wide), medium (2 blocks wide) and small (1 block wide). Big and medium slimes split into smaller versions when killed rather than dying outright, so a flush mechanism (water streams pushing them into a hole) plus damage at the bottom (Magma Blocks, a fall, or a fire trap) is the standard setup. Place the killing block where only the small slimes can reach it so the splits funnel down naturally.
5. Find the right AFK spot — usually 23 to 24 blocks above the farm. Hostile mobs only spawn 24 to 128 blocks from the player, and despawn when you're more than 128 blocks away. Stand too close and slimes won't spawn at all; stand too far and they despawn before reaching the killing chamber. An AFK platform 23 blocks above your room — far enough that the room is in the spawn zone but you're still close enough to keep slimes loaded — gives the most consistent rates.

What You Actually Use Slimeballs For

It's easy to underestimate how much late-game stuff needs slimeballs. Sticky pistons for farms and base mechanisms, magma cream for potions of fire resistance, leads for pets and animals on walks, slime blocks for bouncy builds and piston-powered machinery. If you've been playing on a world for more than a few months and never built a farm, there's a good chance you've got something stuck in your to-do list because "I need more slimeballs first". A confirmed Slime Chunk fixes that for good.