MCA Selector Troubleshooting
MCA Selector won’t start, won’t open your world, or did something you did not expect? Every guide below is organised by symptom and based on the real reports in the project’s official GitHub issue tracker — what actually causes each problem, and the fix that works.
Before you dig in: two checks that solve half of everything
1. Are you on MCA Selector 2.9? The tool has to understand your world’s Minecraft version. Worlds saved by Minecraft 26.3 need 2.9; older tool builds freeze, crash or misread newer saves. Get the current release from the download page first.
2. Is your world backed up? MCA Selector has no undo and no save button — deletions and NBT changes are written to disk the moment you confirm them. Close Minecraft (and stop your server), then copy the whole world folder somewhere safe before you change anything.
It won’t start
Missing JavaFX error
A dialog says JavaFX is missing or cannot be found when you launch the .jar. Your Java runtime lacks the JavaFX toolkit — fix it with a JavaFX-bundled JRE 21 or the official module-path launch command.
MCA Selector not opening at all
Double-clicking the .exe or .jar does nothing, or the window opens blank. Launch it from the command line to see the hidden error — usually a too-old Java, missing JavaFX, or a stale render cache.
Mac problems: won’t open or install
Use the official .dmg that matches your chip (arm64 or x64), get past Gatekeeper the right way, and skip the outdated .jar + manual JavaFX advice from old threads.
Java requirements, explained
Which Java MCA Selector actually needs — 64-bit JRE 21+ with JavaFX, at least 6 GB of RAM — and why the Windows installer lets you skip Java entirely.
The world won’t load
“No Dimensions found”
You selected the wrong folder level. MCA Selector needs the world root folder that directly contains the region and poi sub-folders — and a Bedrock save will always fail this way, because the format is different.
“Open World” does nothing
File → Open World silently ignores you when the saves directory saved in Settings no longer exists. Point it at your real saves folder and the dialog comes back.
Crashes or freezes loading a world
Almost always a version mismatch: the tool is older than the world’s DataVersion. Why snapshot worlds carry no guarantee, and how to tell a damaged save from a broken install.
Edits behaving strangely
Changes “not saving”
There is no save button to forget: deletions and NBT Changer edits write instantly. The real culprits are editing the wrong folder, leaving the world open in the game, or closing the Chunk Editor without pressing Apply.
Only whole regions will delete
You are zoomed out into region selection mode. Zoom in until the chunk grid appears — and read the recovery truth before it happens: an accidental region delete can only be restored from a backup.
Chunk Editor and the Apply button
The one place in MCA Selector where edits are staged: how single-chunk NBT editing works, and why nothing is written until you press Apply.
How to use MCA Selector — the full guide
New to the tool, or want the safe routine end to end? The complete beginner’s guide covers opening a world, selecting, deleting, exporting and editing without the expensive mistakes.
Still stuck after the guide for your symptom? The download page lists the official GitHub repository, where the issue tracker is the fastest route to the maintainer — search it with your exact error text first.