[world_blocks_commands]

How to Use the Fillbiome Command Generator

  1. Enter Corner 1 and Corner 2 – the two opposite corners of the region whose biome you want to change.
  2. Type or pick the target biome id, such as minecraft:plains or minecraft:desert.
  3. Optionally set a replace filter biome – if set, only areas currently matching that specific biome will be changed; everything else in the region is left alone.
  4. Copy the generated /fillbiome command into a command block or the console.

Command Syntax Reference

/fillbiome <from> <to> <biome> [replace <filter>]

/fillbiome sets the biome for every position in the cuboid region between the two corners. Unlike blocks, biomes are stored per 4x4x4 sub-chunk cell (a quarter of the resolution of block coordinates on each axis), so very small or oddly-aligned regions may end up rounding to the same cells as a slightly larger region. With no filter, every cell in the region is overwritten to the new biome. With an optional replace <filter> clause, only cells that are currently the filter biome get changed – cells with any other existing biome are skipped.

Changing a biome with /fillbiome does not retroactively change already-placed blocks, existing grass/foliage colors on rendered chunks (a client may need to reload the chunk to see updated colors), or entities that already spawned – it only affects how the game classifies that area going forward, for things like new mob spawns, ambient sounds, sky/fog color, and future world generation queries in that space.

Frequently Asked Questions

Does /fillbiome change the blocks in the region too?

No – /fillbiome only changes the biome classification of the space, not any blocks already placed there. If you want a visual overhaul (like turning a plains area into a proper desert with sand and cacti), you still need separate /fill or /clone commands to actually change the terrain; /fillbiome alone will leave grass blocks sitting in what the game now calls a desert.

Why do I need to reload chunks to see the new biome’s grass color?

Grass, foliage, and water tint colors are baked into the client’s rendered chunk mesh based on the biome at the time of rendering. Changing the biome server-side with /fillbiome doesn’t automatically force a re-render, so already-loaded chunks can keep showing old colors until the client reloads them (leaving the area and coming back, or using a client-side chunk reload).

What does the optional replace filter actually do?

It scopes the change to only cells that currently match a specific existing biome, leaving every other biome in the region untouched. This is useful for surgical edits – for example, changing only the minecraft:desert patches inside a larger mixed region to minecraft:badlands without touching any plains or savanna cells that happen to be in the same bounding box.

Why does my small fillbiome region affect a slightly bigger area than expected?

Biomes are stored at a coarser resolution than blocks – each biome cell covers a 4x4x4 block volume. Coordinates you give get rounded to the containing biome cells, so a region that doesn’t align to 4-block boundaries ends up affecting the full cells its corners fall inside, which can be slightly larger than the exact block range you specified.

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