Zstd and world rollback
Understand format compatibility before enabling region compression or returning to Paper.
What changes
feature-flags.region-file-compression defaults to true. Writes use the custom checksummed nusaspigot:zstd codec. Existing chunks migrate gradually as they are saved; startup does not convert an entire world at once.
Nusa reads gzip, zlib, uncompressed, LZ4, and its own zstd format. Anvil containers and external .mcc payloads remain supported. The same file extension does not imply every editor/server can read the codec.
Check before returning to Paper. Unmodified Paper and tools without the custom codec cannot read Nusa zstd chunks. Disabling the flag selects Paper’s writer for future saves; it does not convert existing zstd data.
Plan the migration
Back up the stopped server before the first Nusa run. If straightforward format rollback is a requirement, set the compression flag false before opening the old world. Test this on staging.
Higher compression levels may increase CPU work. Start with level 3 and measure. The accepted range is -5..22; see storage settings.
If the world already contains zstd
Restore a pre-migration backup, or completely convert all affected data using a tool that explicitly supports this codec and verify the result. The project does not include a production world converter.
Do not open your only world copy with an unsupported reader. Safemode, disabling the writer, or saving a few chunks does not convert every region. Preserve the original and experiment only on copies.