Biome Cleaner

Small biome regions are merged into the larger neighboring biome, which gives the world cleaner boundaries. Terrain shape, structures and gameplay stay as they are; only the biome assignment changes. With default settings, isolated single-chunk fragments of plains inside a forest and awkward beach slivers are absorbed by the surrounding biome.

The mod is configurable. A size limit decides when a biome region counts as too small to keep, and biome groups allow bulk settings such as treating all ocean variants together. Individual biomes can be protected so rare ones are never replaced, or prevented from spreading into other areas. Oversized regions can be trimmed down to a maximum size instead of being replaced outright, and a boundary rule can force a biome to be cleaned up when it does not touch the right neighbors, for example removing inland beaches that sit next to ocean or river.

Chunks are cleaned in background threads ahead of the player, so new terrain loads without added lag, and the server's tick rate is not affected. The mod runs on the server alone, and players need nothing installed on their side. Files are published for Fabric, Forge and NeoForge for game versions 1.21.1 – 26.1.2, under the MIT License, which is not open source.