Want a plains base in a desert, or a frozen harbour where the game generated a warm ocean? MCA Selector can rewrite a chunk’s biome — with one important limitation you need to understand first: in the current tool, a biome change applies to the whole chunk at once. There is no biome brush. Here is the exact path, and what to do when a whole chunk is too coarse.
Back up your world first: MCA Selector writes deletions and NBT changes straight to disk the moment you confirm them — there is no undo and no File → Save step to catch a mistake. Close Minecraft (and stop your server, if the world is on one), then copy the whole world folder somewhere safe before you edit.
The tool for the job: the NBT Changer’s Biome field
MCA Selector changes biomes through the NBT Changer, its batch NBT editor. Among its fields is Biome, which sets the biome of every selected chunk to a single value. The workflow:
- Open the world (game closed) and select the chunks whose biome you want to change — by dragging on the map, or by filter if you want, say, only chunks currently of a certain biome.
- Open the NBT Changer and find the
Biomefield. - Enter the target biome by name or ID (for example
minecraft:snowy_plains). A custom biome from a datapack or mod is entered in single quotes. - Make sure the change is limited to your selection if you do not want it applied more widely, then run it.
Like almost everything in MCA Selector, the change is written to the world files as soon as it runs — no Save step, no undo. If you are new to the NBT Changer, the NBT Changer guide explains its Change vs Force modes and its other fields before you touch a real world.
What a whole-chunk biome change does and does not do
- It changes the biome data — grass and leaf colours, precipitation (rain vs snow), ambient effects and biome-dependent spawning rules follow the new biome.
- It does not change a single block. Sand stays sand and water stays water; only the biome label changes. Reshaping the terrain itself is a different job (delete and regenerate, or edit in game).
- It is all-or-nothing per chunk. A chunk that straddles a riverbank gets one biome everywhere, including the parts that looked right before.
- Already-generated structures and features stay. Changing a chunk to a biome does not retroactively add that biome’s structures.
Finer control: per-section changes need a script
Under the hood, a chunk stores biomes per 16-block-tall section, in a biomes palette. The NBT Changer’s single Biome field deliberately collapses that to one value. If you truly need different biomes in different sections of a chunk, the official route is a Groovy script in the NBT Changer’s custom/script support that rewrites the sections’ biome palettes directly — the official wiki’s custom filter tutorial shows the pattern. That is power-user territory: test any script on a throwaway copy of the world first, on a handful of chunks, and check the result in game before running it widely. The single-chunk Chunk Editor is the other manual option for inspecting what a chunk actually contains.
Verify the change
- Open the world in Minecraft and go to the edited chunks.
- Press F3 and read the biome shown on the debug screen while standing in the chunk — it should report the new biome.
- Check the visible tells: grass colour, and whether precipitation and foliage match the new biome.
- Walk across the chunk border to confirm neighbouring chunks were not changed by accident.
If the F3 screen still shows the old biome, the usual causes are that the change was applied to a different selection than you thought, or the world was open in the game while you edited and overwrote it — close everything, restore the backup, and redo it on the copy first.
Download MCA Selector 2.9
Everything in this guide works with the current release. Get the Windows installer, the cross-platform .jar, the macOS .dmg or the Linux .deb/.rpm from the MCA Selector download page — every button there points at the official GitHub release files and lists the SHA-256 checksum, with a clearly labelled site mirror as a fallback.
One last backup reminder: keep the copy of your world you made before editing until you have loaded the edited world in Minecraft and confirmed it looks right. Deletions and NBT changes in MCA Selector are permanent once applied.