Biomes are 3D now: why the biome under your feet is not the one on the surface
Cave biomes generate independently of the surface, which changes mob spawns, water colour and where structures appear. What that means in practice.
Biomes used to be a flat map: one biome per column, top to bottom. They are now volumetric, and a lot of confusing behaviour falls out of that one change.
Surface and cave biomes are separate
Standing in a plains biome and digging down, you can pass through Dripstone Caves, Lush Caves or Deep Dark without the surface biome changing at all. F3 reports the biome at your position, not the column's.
Consequences:
- Mob spawns change with depth. Glow squid in Lush Caves under a desert. Wardens under
a taiga.
- Structures follow the cave biome. Ancient Cities generate in Deep Dark wherever it
occurs, regardless of what is above.
/locate biomegives a Y. It returns a 3D position because a biome now has one.
What each biome actually controls
| Property | Note |
|---|---|
| Mob spawn lists | per-biome, with separate lists per category |
| Grass and foliage colour | computed from temperature and downfall, not stored directly |
| Water and fog colour | stored per biome |
| Precipitation | rain, snow, or none — driven by temperature |
| Structure eligibility | most structures are gated on a biome tag |
The colour one surprises people: grass in a swamp is a different green because of temperature and rainfall values, not because the game stores "swamp green". That is also why the transition between biomes blends rather than snapping.
Temperature is by altitude too
Snow forms above a temperature threshold that falls as Y rises. That is why the same mountain has grass at the base and snow at the peak inside one biome, and why placing water high up freezes when the same water at sea level does not.
Mob variants are biome-driven
Several mobs pick their look from where they spawn:
- Axolotl — five colours, blue only from breeding, never natural
- Frog — temperate, warm or cold, decided by the biome the tadpole grows up in,
not where the egg was laid
- Rabbit, fox, llama, cat — coat by biome or structure
- Tropical fish — 2,700 combinations, biome-weighted
Frogs are the practical one: move tadpoles to the biome you want before they mature.
Changing a biome in place
/fillbiome ~-32 ~-32 ~-32 ~32 ~32 ~32 minecraft:lush_cavesWorks on a region and takes effect immediately for spawns, but existing blocks do not change — grass stays the old colour until the chunk is relit, and clients may need a rejoin to update tint. Useful for map-making, disorienting in survival.
Browse every biome with its spawn list and features, plus each mob's texture and behaviour variants, in the Biome & Mob Variant Browser.