Drop a datapack .zip here
or
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Technical detail
Is the pack itself well-formed?
MCJIG says what a pack will build. When it cannot say anything, the next question is whether the pack is valid at all — which is what MCDDD, its companion, exists to answer. It can run right here on the file you already dropped, without uploading it or making you find it again.
Placement is random. One run says almost nothing, so the numbers are rates across seeds and the view lets you step through them.
Simulating…
Drag to orbit, wheel to zoom, click a box to name it. Hide pools and pieces from the panel on the right to see the structure itself. Open full screen
The full report
Graph check
Faults provable without simulating: things the pack claims and cannot deliver. These are decidable and seed-independent, so they are never false positives.
MCJIG , a jigsaw structure generation simulator. Companion to MCDDD: MCDDD tells you a pack is well-formed, MCJIG tells you what it will build.