MCA Selector can remove selected chunks from a Minecraft Java Edition save so those locations can generate fresh terrain the next time they are visited. It is an external desktop editor, not an in-game command. The safe method is to stop Minecraft, make an untouched backup and a separate working copy, open the working copy in a build that supports the save’s data version, select only expendable chunks, delete them, and test the result before replacing the live world.
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The operation is powerful but destructive. The MCA Selector project warns: “MCA Selector modifies and deletes chunks in your Minecraft world. Please make backups of your world before using.” Treat that warning literally: a deleted chunk can lose its blocks, entities, containers, structures and portal pieces, and recovery depends on the backup you kept.
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What MCA Selector does
MCA Selector edits the region and chunk files in Minecraft Java Edition world saves. It can export, delete or otherwise edit selected chunks and regions from outside the game. Because it works on save data rather than a running server, it cannot safely be used while Minecraft or a server process is writing to the same world.
A Minecraft world is divided into chunks. When you delete a chunk with MCA Selector, its saved terrain and contents are removed from the save. If Minecraft later visits that coordinate, the game can generate replacement terrain there. This is why trimming is useful after a major update or after players explore far beyond the areas they actually use: old, unwanted terrain can be removed and regenerated later under the version you choose.
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Deletion does not understand your intentions. A chunk that looks empty on the map may contain an underground storage room, a redstone circuit, a villager trading hall, a portal connection or the end of a rail line. The map is an aid to selection, not proof that a chunk is disposable.
When trimming is useful
Trimming is most useful when a save contains large areas that were generated during exploration but are no longer needed. Removing those areas can reduce the amount of saved world data and provide a clean regeneration boundary for a newer Minecraft version. It is also a way to discard accidental exploration corridors while preserving a compact core around bases and infrastructure.
No independent storage-reduction percentage or performance guarantee is established for MCA Selector. The amount reclaimed depends on which chunks you remove and how much data those chunks contain. Keep the original save even if the edited copy appears to work; the untouched copy is your only straightforward recovery path.
Before opening a world
Stop every process that can write to the save
Quit Minecraft completely. For a multiplayer world, stop the server and wait until its process has finished writing. Do not leave a launcher, backup job or synchronization tool modifying the folder while MCA Selector has it open. Editing a live save can produce inconsistent files or overwrite your changes.
Create two copies
- Locate the complete world folder, including its region data, player data, dimensions and metadata.
- Copy that folder to a separate backup location and label it as the untouched original.
- Make a second copy for editing. Open only this working copy in MCA Selector.
- Keep the original backup until the edited copy has been opened in Minecraft and thoroughly checked.
Do not edit the only copy, and do not rely on a partial backup of just the Overworld. Nether and End data live in separate dimension directories and must be preserved or copied independently.
Record what must survive
Before selecting anything, make a short list of coordinates and routes that matter. Include your main base and spawn area, villages you use, farms, storage rooms, rail and ice roads, nether portals and their Overworld links, redstone machinery, map-art areas and temporary staging sites that still contain supplies. Screenshots or written coordinates make the later review much safer.
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Choose a compatible MCA Selector build
Download MCA Selector from the official Querz/mcaselector GitHub project. The project publishes version 2.9 packages for Windows, macOS arm64 and x64, Debian, RPM-based Linux systems and a universal JAR. Choose the package appropriate for your operating system rather than an unofficial mirror.
Compatibility is tied to the Minecraft save’s data version, not merely to the name you give the world. Check the version in which the world was last saved, then compare it with the project’s supported-version table before opening the folder.
| Minecraft save status | What the official table indicates | Practical action |
|---|---|---|
| Released versions | Minecraft 1.2.1 through 1.21.11 are listed. | Use an MCA Selector build that lists your save’s data version and verify the world on a copy. |
| Development versions | Development 26.1 through 26.3+ are listed. | Match the development build precisely and expect changes between releases. |
| Old or unlisted snapshots | Snapshots are not guaranteed to be supported. | Do not assume a snapshot save is safe to open; retain the original and test with a disposable copy. |
If the installed application does not list the save’s data version, stop rather than guessing. A version mismatch can prevent the tool from interpreting chunks correctly. The supported-version table and release documentation are the authority for the build you install.
Open the working copy and the right dimension
- Launch MCA Selector after Minecraft and any server process are stopped.
- Use the open-world command to choose the working copy, never the untouched backup.
- Confirm that the displayed folder is the copy you intended to edit. Check the path and, if necessary, add a temporary marker to the copy’s folder name before opening it.
- Decide which dimension you are working on. The Overworld, Nether and End have separate region data, so inspect and trim them as separate maps.
Do not assume that removing an Overworld chunk removes its Nether counterpart or a portal destination. Each dimension requires its own review. A portal route can fail even when the visible base is preserved if its linked portal or approach route is in a removed chunk.
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Manual selection for irregular areas
Use the map to draw a selection around areas you know are expendable. Manual selection is the best choice when a world has irregular boundaries: a base surrounded by farms, a winding rail line, scattered outposts or several small builds. Leave a generous margin around every protected coordinate until you have checked the exact chunk boundaries.
Chunk boundaries do not always match the outline of a build. A structure near an edge can occupy more than one chunk, and a road can cross many chunks. Select by the complete footprint of the thing you are protecting, not by the chunk that contains its center.
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Chunk Filter for repeatable rules
MCA Selector’s Chunk Filter can identify candidate chunks using rules such as light inhabitation or other properties exposed by the tool. Filtering is faster than hand-drawing thousands of chunks and is useful for repeatable maintenance, but it is not an automatic safety decision. A lightly inhabited chunk may still contain a valuable farm, portal, storage cache or transport link.
Run the filter, inspect every candidate against your coordinate list and remove candidates that intersect protected areas. Save a record of the criteria you used so a later cleanup can be compared with the earlier one.
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| Selection approach | Advantage | Risk and review requirement |
|---|---|---|
| Manual map selection | Maximum control around bases, corridors and unusual layouts. | Slow for large areas; missed edge chunks can leave unwanted terrain behind. |
| Chunk Filter | Fast, repeatable identification of rule-based candidates. | A rule cannot know which apparently empty chunk matters to you; inspect every result. |
| Conservative criteria | Leaves more terrain and lowers the chance of accidental loss. | Reclaims less space and may require another cleanup later. |
| Aggressive criteria | Can reclaim more space in one pass. | Requires much more coordinate checking and carries greater loss risk. |
The official wiki documents Selections and Chunk Filter, but it does not publish a universal safe distance or time threshold. Do not adopt a tutorial’s claim that a particular radius or age is always safe; choose boundaries from your own builds and routes.
Chunks that should normally be protected
- Spawn and player bases: include the complete footprint, underground levels and surrounding access.
- Villages and trading areas: villagers, beds and workstations may be spread across adjacent chunks.
- Farms: protect crop, mob, tree, animal and item-collection areas, including redstone and loading zones.
- Storage: keep warehouses, shulker caches, temporary chests and hidden emergency supplies.
- Transport: preserve rail lines, ice roads, bridges, stations and the chunks needed to approach them.
- Portals: protect both portal structures and the routes that connect them in each dimension.
- Redstone and technical builds: a machine can extend underground or across chunk borders even when little is visible on the surface.
- Map art and landmarks: large images and decorative layouts often occupy more chunks than expected.
- Staging areas: temporary construction camps may still contain materials, beds, villagers or navigation markers.
When uncertain, exclude the chunk from the deletion set. A larger retained area is easier to trim later than a lost build is to reconstruct.
Delete selected chunks on the working copy
- Recheck the selection overlay against your protected-coordinate list.
- Confirm that the active world path is the working copy and that the correct dimension is displayed.
- Use MCA Selector’s Selection delete command.
- Wait for the operation to finish before closing the application or copying files.
- Keep the untouched backup unchanged and clearly labeled.
For the edited copy, treat deletion as irreversible. Saved blocks, entities, inventories, containers, structures and portal components inside removed chunks may no longer exist. MCA Selector’s warning is the reason to maintain the original rather than relying on an undo feature or a second pass.
Test regeneration before going live
Open the edited copy in the same Minecraft version used to interpret the save. Visit several coordinates that you deliberately deleted, including points near the retained boundary. Minecraft can generate replacement terrain when those locations are visited again.
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What to inspect
- Check that new terrain appears where the deleted chunks were expected to be regenerated.
- Walk along the boundary and look for unexpected seams, abrupt terrain changes or missing sections of a road.
- Visit every preserved base, farm, storage room and portal route that borders the deletion area.
- Verify that entrances, bridges, rail lines and Nether connections still lead to the intended coordinates.
- Check player inventories, containers and important entities in retained chunks.
Test more than one deleted location. A single successful regeneration visit does not prove that every selected region was correct. If you find a missing build or broken route, close Minecraft without saving further changes, restore the untouched backup and repeat the selection with a larger protected margin.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Put the edited world into production
Only after the copy passes your checks should it replace the live save. Stop Minecraft or the server again, move the current live folder out of the way as an additional rollback copy, and place the tested edited folder where the game or server expects the world. Start the world and perform a final check of the primary base and travel routes.
Keep the untouched original and the pre-replacement live copy for as long as your normal backup policy requires. Do not delete them immediately after the first successful launch; problems can appear only when a distant area, portal or farm is used later.
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If you need repeatable or headless cleanup, the MCA Selector wiki includes a CLI Mode page. Use the CLI documentation that belongs to the release you installed because flags and syntax can change. Build a script around a working copy, log the selected coordinates and retain the original backup. An old tutorial’s command line should not be treated as current documentation.
A scheduled cleanup should still include a stop or quiescence step for the server, a complete copy of the world and a validation launch. Automation makes selection repeatable; it does not make an unsafe rule safe.
Troubleshooting common problems
The world will not open in MCA Selector
Confirm that you selected a Java Edition save, that the folder is a complete world copy and that the MCA Selector release supports its data version. If the save comes from an old snapshot or an unlisted development build, compatibility is not guaranteed. Do not experiment on the only copy.
The wrong world or dimension is displayed
Close the tool, verify the folder path and reopen the intended working copy. Then select the correct dimension’s data. Overworld, Nether and End regions are separate; editing one does not select the others.
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Deleted terrain does not regenerate immediately
Regeneration occurs when Minecraft revisits the deleted coordinates. Travel into the area in the edited copy and allow the game to load it. If a location still contains its old terrain, verify that the correct chunk was selected and that you opened the edited folder rather than the untouched backup.
A preserved build is missing
Stop using that edited copy and restore the untouched backup. Review the build’s full footprint, adjacent chunks and any dimension counterpart, then repeat the operation with a wider exclusion area. Do not keep playing and hope a later regeneration will restore saved blocks; deletion removed them from that copy.
A route or portal is broken
Inspect both ends of the route and every intermediate chunk. Rail, ice-road and portal approaches frequently cross chunk borders. Restore from backup if any required section was deleted, then protect the entire connection in the next selection.
Practical decision checklist
- Is the game or server stopped and no process writing to the save?
- Do you have a complete untouched backup and a separate working copy?
- Is the installed MCA Selector build compatible with the save’s data version?
- Have you recorded coordinates for bases, farms, storage, portals, transport and technical builds?
- Did you inspect filtered candidates manually instead of trusting the rule alone?
- Did you review each dimension independently?
- Did you test deleted locations and preserved borders in the same Minecraft version?
- Did you retain rollback copies after promoting the edited world?
If any answer is no, postpone deletion and correct that item first. The time saved by skipping a check is small compared with rebuilding a deleted base or restoring a damaged save.
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