Slime Chunk Spawning Rules
A chunk is a slime chunk when the seeded slime-chunk random gives zero out of ten. In a slime chunk, a slime can spawn below Y 40, and only one in ten spawn attempts there passes the slime check. Slimes do not spawn on Peaceful difficulty.
Surface Spawning in Swamps
Surface slimes spawn only in swamp and mangrove swamp biomes, between Y 51 and Y 69. The surface slime spawn chance follows the moon phase: 0.5 at full moon, 0.375, 0.25, 0.125, and 0 at new moon. A surface slime also needs the light level at its spot to be no higher than a random number from 0 to 7.
Slimes from a spawner skip the slime chunk and swamp rules and use the normal mob spawn rules.
Using Our Slime Finder
Our interactive Slime Finder calculates candidate coordinates directly in your browser.
- Open our Slime Finder companion tool.
- Enter your world seed and select your Minecraft game version.
- Locate your current in-game coordinates using the search box.
- The interactive map highlights candidate coordinates in green.
Our companion Seed Map and Biome Finder display continent terrain and surrounding biomes.
Sources
Read from the official 26.3 server jar (Slime.checkSlimeSpawnRules, data/minecraft/timeline/moon.json, biome tag allows_surface_slime_spawns).