“Resetting” a chunk in Minecraft means deleting it so the game generates it again from scratch — with the terrain, ores and structures of the version you are running now. It is how old worlds get new-update caves, ores and biomes without starting over. MCA Selector does not have a separate reset button: a reset is a delete with a plan, and this guide is that plan.
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.
How resetting works
A chunk exists on disk only because it was generated and saved. Delete it in MCA Selector and the next time a player enters that area, Minecraft generates a brand-new chunk from the world seed using the current version’s generator. Three consequences follow:
- Everything in the chunk is gone: builds, chests and their contents, containers, entities that were saved with it.
- The new chunk matches the current game version — new ores, caves and structures can appear.
- The new chunk may not blend smoothly with the old terrain around it; expect visible borders on dramatic generation changes.
Step 1: Decide what is safe to reset
The workhorse for this is the InhabitedTime field: how long players have spent in a chunk, stored in game ticks (20 ticks = 1 second, so one hour in a chunk is 72,000). Chunks a player merely flew over on the way somewhere typically show a tiny InhabitedTime; chunks containing bases, farms and storage show a large one. Resetting low-InhabitedTime chunks refreshes the exploration filler around your world while leaving lived-in areas untouched. It is a heuristic, not a guarantee — a chunk can hold a small outpost a player built in ten minutes — so combine it with a look at the map.
Step 2: Select the chunks to reset
- Open the world (File → Open World) with the game and server closed.
- Open the chunk filter and set a condition on
InhabitedTime— for example, only chunks below a threshold you choose based on how your players actually play (start conservative). - Optionally add a
DataVersioncondition so you only touch chunks generated by older game versions; the DataVersion list shows which values belong to which Minecraft version. - Apply the filter to build the selection, then zoom in and eyeball the borders of the selection near your bases before deleting anything.
- Export the selection (Selection → Export selection) as a CSV so the reset is documented and repeatable.
Step 3: Delete, then let the game regenerate
Run Selection → Delete selected chunks. Deletion is instant and permanent — there is no separate “regenerate” step inside MCA Selector. Regeneration happens later, in Minecraft, when someone loads the area. The mechanics are the same as the delete chunks guide; if you are resetting everything outside your kept areas for a major update, the pruning workflow wraps this into a complete procedure.
Protect these areas — a pre-reset checklist
- Main bases, storage systems and farms in every dimension you edit — check Overworld, Nether (travel hubs and tunnels are easy to forget) and End separately.
- Spawn point surroundings and any spawn builds.
- Community areas on servers: shops, mini-game arenas, other players’ projects.
- Chunks containing portals your players rely on — the portal in the other dimension can end up orphaned.
- Anything marked on maps or in screenshots that you cannot locate on the MCA Selector map — find it first, reset later.
Step 4: Verify in game
Load the world, visit a reset area, and confirm the new terrain generates with the expected features of your current version. Check the seams around kept areas. If something important was reset, restore the backup copy — which is why the backup from the top of this guide is not optional.
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.