Minecraft Random Sequence

Random Sequences

This content applies only to Java Edition.

Random sequences provide controllable randomization via random number generator sequences.

Storage format

File: <save root>/data/minecraft/random_sequences.dat (GZip NBT):

• Root tag
  • data (compound, required):
    • include_sequence_id (bool): whether the sequence namespace ID participates in seeding; modifiable by /random reset *; absent = true.
    • include_world_seed (bool): whether the world seed participates; absent = true.
    • salt (int): salt for initialization; absent = 0.
    • sequences (compound, required): created sequences.
      • <namespace ID> (compound): one sequence with source (long array, required): seed low 64 bits + high 64 bits.
  • DataVersion (int): absent = 1343 (Java 1.12.2).

Creating sequences

Parameters: identifier, worldSeed, salt. The game uses Xoroshiro128++ with a 128-bit seed:

long initialSeed = salt;
if (include_world_seed) initialSeed ^= worldSeed;
long unmixedLo64 = initialSeed ^ 0x6A09E667F3BCC909L;
long unmixedHi64 = unmixedLo64 + 0x9E3779B97F4A7C15L;

If include_sequence_id, the MD5 of the identifier is XORed into both halves. Then both halves are mixed with mixStafford13 ((l ^ l>>>30) * 0xBF58476D1CE4E5B9L, then (l ^ l>>>27) * 0x94D049BB133111EBL, then l ^ l>>>31). A zero seed is replaced with low −7046029254386353131L / high 7640891576956012809L.

Behavior

Missing/incomplete files initialize with include_sequence_id=true, include_world_seed=true, salt=0. Each use consumes and updates the sequence. Most loot table calculations use random sequences (block drops, mob drops, fishing, piglin bartering); world-gen loot chests are directly seed-controlled instead.

/random reset resets a sequence with the given parameters; /random reset * resets all and syncs parameters into the file.