Trim your world with MCA Selector

A world grows every time a player explores new ground, because the game saves the world's chunks in region files. If your world is taking up too much disk, MCA Selector can delete chunks nobody has spent time in. A deleted chunk is generated again the next time a player loads that area. MCA Selector is a free desktop tool that works on a copy of your world on your own computer, so you download the world, trim it and upload it again.

Checked against MCA Selector 2.9 on Minecraft 26.3, October 2026.

Check what is using the disk

Open the Disk Analyser tab. It shows how much disk each folder uses. Trimming only helps if the world folder is the big one. If it is plugins or a backups folder made by a plugin, start there (Fix: server out of disk space).

What you need

• MCA Selector from the releases page on GitHub. There is a Windows installer, macOS and Linux packages, and a universal jar. The tool's own notes say version 2.9 supports Minecraft 26.1 to 26.3 and that 2.7 added the newer dimensions folder layout.
• Java 21 or newer with JavaFX if you use the jar. The Windows installer packs everything it needs. The wiki asks for at least 6 GB of RAM, with 4 GB assigned.
• Enough space on your computer for a copy of the world.

Download a copy of the world

1. Open the Backups tab and press Create backup. Create and restore backups has the steps.
2. Press Stop on the Console tab.
3. Open the File Manager, select your world folder (world unless you changed World folder in the Config Editor) and press Download. The panel packs a folder into a .zip first, on the server, so this fails if the disk is full. In that case fetch the folder over SFTP instead (Connect over SFTP).
4. Unpack it on your computer.

Choose the chunks to delete

1. In MCA Selector, open the File menu and choose Open World. Pick the world folder itself, the one that holds level.dat, not a region subfolder. Since version 2.7 it finds the dimensions inside the newer dimensions/minecraft/<dimension_name> folder layout. If it shows a Select Dimension window, choose one. You can open the others later.
2. Open the Tools menu and choose Filter chunks.
3. Add a condition. Set the type to InhabitedTime, which is the time players have spent in a chunk in game ticks, about 20 per second. Choose the < comparator and a short time such as 5 minutes, so only chunks nobody lingered in match.
4. Press Select, not Delete. This marks the matching chunks without changing any file.
5. Look at the map. Your builds and spawn must not be highlighted. Adjust the condition until they are clear.

Delete and check the size

1. Open the Selection menu and choose Delete selected chunks, then confirm "You are about to delete N chunks from this world". The wiki warns that deletion is instant and cannot be undone, which is why you work on the copy.
2. Check the size of the world folder on your computer. MCA Selector deletes a region file outright when every chunk in it is selected, and otherwise rewrites the file without the deleted chunks, which is what makes the folder smaller.
3. If you also use the Nether or End, repeat for each dimension with File, then Open Dimension.

Put the trimmed world back

Choose one:

• Smaller worlds. Zip the folder, stop the server, and use World Import (Upload your singleplayer Minecraft world). The import unpacks the zip next to your old world before swapping it in, so you need room for the zip, its unpacked copy and the old world, and the old world is kept as world.pre-import-<date>. The import always installs the world as world and sets level-name to world, so if you use a different World folder, upload the .mca files over SFTP instead. Delete the kept folder in the File Manager afterwards, because that is what frees the space.
• Disk nearly full. Upload the trimmed .mca files into the matching region folders over SFTP, replacing the old ones (Connect over SFTP). Browser uploads stop at 100 MB per file. Fix corrupted chunks and region files lists the folders for each version.

Start the server and check the Disk Analyser again. To stop the world growing again, Set a world border.