Worlds grow every time someone walks somewhere new, and they never shrink on their own. A world that is mostly one player's shopping trip from two years ago can be cut down substantially — carefully.
Why it happens
Every 512×512 block area of terrain that anyone has visited is stored as a region file, named for its coordinates like r.3.-2.mca. Those files never get smaller and are never removed, so a world's size reflects everywhere anyone has ever been, not where anyone still goes.
What to do
- Take a backup and download it
This is a destructive operation on the only copy of your world. Not a backup on the server — a backup on your own machine.
- Work out what to keep
Spawn, the main builds, and a generous margin. Ask players for coordinates of anything they care about before you start, not after.
- Use a region-editing tool
Offline tools let you select the chunks to keep on a map and delete the rest. Doing this by hand from filenames is possible and is how mistakes happen.
- Set a world border afterwards
Otherwise the same growth starts again the same evening. A border is what makes the trim last.
- Test on the copy first
Load the trimmed world on a test instance and walk around before it becomes the live one.
There is no per-build check. If someone built a base at the edge of what you cut, it is gone with the terrain, and no amount of regenerating brings it back — the new terrain will not even match the old. Ask first. Every time.
If the growth is from mining, a separate resource world that gets reset on a schedule keeps the main world small permanently. That is prevention rather than cleanup, and it never involves deleting anybody's work.
Common questions
- Does trimming improve TPS?
- Usually not. Unloaded chunks cost nothing to tick. It saves disk space and makes backups faster.
- Will trimmed areas come back if someone walks there?
- Yes, as newly generated terrain — which may not match the old at the seams.
- How much can I expect to save?
- On a world where people explored widely, often more than half.