Pair the correct files first
Choose the current MCA and a real backup from the same world, dimension and region coordinates. Matching filenames alone do not identify a world. When recognized region filenames or chunk xPos/zPos tags provide coordinates, the tool checks them and refuses a known mismatch. Missing coordinate evidence is reported so that you can verify the pairing yourself.
Select one to 32 slot numbers. Each requested backup record must have a supported compression method and decode into bounded Java NBT before it can be copied. The selected current record may be damaged; recovery does not require that damaged payload to parse successfully. An empty or invalid backup slot cannot recreate the missing data.
Understand the append-only output
The output starts as a copy of the current region. Verified backup records are appended in newly allocated sectors, then only the selected location and timestamp entries are updated. Original sectors and every unselected header slot remain byte-for-byte intact. Old selected sectors remain in the file as unused data, so the resulting file can grow.
For example, restoring slot 33 changes the reference for local coordinates 1,1 and its timestamp. It does not rewrite slot zero or clean up unrelated allocation problems. The report lists remaining header issues explicitly. This is selective record replacement from evidence, not automatic reconstruction of a whole world.
Test a separate world copy
The resulting region must stay within 32 MiB; selected backup data also has an aggregate expanded-size budget. There is no automatic compaction, cross-version migration or reconciliation of separate entity and point-of-interest regions. A chunk restored from an older backup can disagree with neighboring terrain, inventories or other saved state.
Close the game, preserve the originals and place the downloaded region only into a separate world copy. Check the restored location and surrounding area using the intended game version. Keep both source files and the JSON restore report so the operation can be reviewed or reversed. Without a suitable backup, this tool cannot invent lost buildings or overwritten chunk contents.