Farm planning
What a slime chunk is
Minecraft splits the world into chunks that are 16 blocks wide and 16 blocks long. In Java Edition, the game mixes the world seed with each chunk’s X and Z and runs a deterministic check. About one chunk in ten passes. The pattern looks random, but the same Java seed always produces the same slime-chunk layout.
A green square is not a promise that slimes are standing there now. It marks chunks where underground slime spawning is allowed below Y=40, typically on platforms at Y=39 or lower, with space, player distance and the hostile mob cap still applying. Light does not block slime-chunk spawns, which is why farms often light the floors to suppress other hostile mobs.
Do not confuse this overlay with surface swamp spawning. Swamp slimes use a separate set of biome, height, light and moon rules. The overlay describes the underground slime-chunk mechanic used for most farms.
How to use this slime chunk finder
- 01Copy the world seed with /seed, including the minus sign when the seed is negative.
- 02Paste it above and press GO. Keep the Overworld selected; slime chunks are an Overworld rule.
- 03Use Java Edition. The current overlay does not support Bedrock slime chunks.
- 04Look for the green overlay on the map. Hover to read block coordinates and the chunk origin (multiples of 16).
- 05Confirm the chunk with F3+G. Keep spawning positions below Y=40 and allow enough clear space for slimes, including large ones.
- 06Test one chunk before building a large farm. Check player distance and nearby naturally spawning hostile mobs that can fill the mob cap.
Java slime chunks and Y=40
The Java slime-chunk test is seed- and coordinate-based. Changing between supported Java versions should not move the green squares for the same numeric seed, though the terrain around them will. Build spawning spaces below Y=40. Y=39 is the usual floor height discussed in farm guides.
Bedrock slime chunks are not the Java map
Bedrock uses a different, seed-independent slime-chunk pattern. This overlay currently supports Java only. You can open our full Bedrock map for biomes and supported structures, but it does not display Bedrock slime chunks.
Farms, swamps and the mob cap
A correct chunk is only the first requirement. You still need spawnable blocks, player range, and usually a way to suppress other hostile mobs. Surface swamp farms are a different project: they care about swamp biome, moon phase and light, not the green overlay. Mixing the two rules is the usual reason a farm stays empty.
When the overlay looks wrong
Check seed, edition and that you are in the Overworld. Mods, datapacks and custom generation can ignore vanilla slime rules. If Java green squares match a known calculator but Bedrock survival does not, you are probably using the wrong edition overlay.
Slime chunk finder FAQ
How many chunks are slime chunks?
In Java, about 10 percent of chunks pass the check. A small area can have more or fewer than one in ten. Bedrock uses a separate fixed pattern.
Which Y level should I build at?
For Java slime-chunk spawning, use Y=39 or lower so the spawn position is below Y=40. Other mob-spawning rules still apply.
Do slime chunks change with the Minecraft version?
The Java slime-chunk hash is stable across supported versions for the same seed. Terrain and caves around the chunk still follow the selected version.
Can I use this for Bedrock?
The slime overlay currently supports Java only. The Bedrock control opens the full Bedrock biome and structure map without a slime overlay.
Why are there no slimes in a green chunk?
The chunk is eligible, not populated. Check height, space, player distance, mob cap, and that you are not mixing swamp-surface rules with slime-chunk rules.
Does light stop slime-chunk spawns?
Light does not disqualify Java slime-chunk spawning. Lighting platforms can reduce other hostile mobs while leaving slimes possible.
Is the seed uploaded?
No. Overlay calculation runs in the browser.
Related planning tools
Other finders
Map and coordinate reports
For a missing or misplaced result, include the full seed, Java or Bedrock, game version, dimension, coordinates, and what appeared in the world. Mention mods, datapacks, add-ons, experiments, server software, or old chunks when relevant.
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