Reference Supported versions

Supported versions

The versions Falco is built against, the versions it accepts, and the floors it refuses below.

This page is a generation target, currently written by hand. Source of truth: the version catalog and Java toolchain in the Falco build, and the constants in FalcoAnvilLoader.

Build and runtime

	Value	Note
Java	25	required to build Falco and to run it
Minestom	2026.06.20-26.1.2	the version every claim in this wiki was checked against; compileOnly, so a consumer picks its own

Chunk data version floor

Constant	FalcoAnvilLoader.DEFAULT_MINIMUM_DATA_VERSION
Value	2844
Corresponds to	Minecraft snapshot 21w43a
Builder slot (read side)	minimumDataVersion(int)
Builder slot (write side)	dataVersion(int) — stamped into every saved chunk; unrelated to the floor
Enforced by	ChunkVersionPolicy, by default DefaultChunkVersionPolicy

21w43a is where a chunk's data moved out of the Level compound onto the root compound, under the key sections (FalcoAnvilLoader.SECTIONS_KEY).

What the guard does with each case

Stored state	Result
No sections, but a Level compound	refused — pre-21w43a layout, whatever DataVersion says
Current layout, DataVersion absent	accepted
Current layout, DataVersion wrong type	refused
Current layout, DataVersion negative	refused
Current layout, DataVersion below the floor	refused
Current layout, DataVersion at or above the floor	accepted
Status: minecraft:full with neither sections nor Level	refused, MISSING_OR_MISTYPED_KEY
Current layout, empty sections list	accepted

Compression schemes

Id	Scheme	Read	Write
1	gzip	yes	no
2	zlib	yes	yes — always
3	uncompressed	yes	no
4	LZ4	no	no
127	custom	no	no

The external bit 0x80 is masked off. Any other id raises The compression scheme <id> is not supported. Only gzip (1), zlib (2) and none (3) can be read (ChunkCompression#fromId).

World directory layout

Layout	Path resolved from the world root
26.1 and later	worldRoot/dimensions/<namespace>/<value>/region
pre-26.1	worldRoot/region — used only when the above does not exist

Related: Explanation The chunk version guard · How-to Migrate a world from an older version · Reference Modules and coordinates