MCUtility

Minecraft UUID format

A Minecraft UUID is a 128-bit number. Java Edition writes it in four different ways, all meaning the same value. Accounts get random version 4 UUIDs; offline-mode players get name-based version 3 UUIDs.

Java Edition · Published

The four forms

All examples below are the same UUID, belonging to Notch’s account.

FormExampleUsed in
Hyphenated069a79f4-44e9-4726-a5be-fca90e38aaf5Commands and target selectors, whitelist.json, ops.json, ban lists, most plugins
Without hyphens069a79f444e94726a5befca90e38aaf5Mojang’s web services, skin texture data
Int array[I; 110787060, 1156138790, -1514210135, 238594805]Entity and player data (NBT) since Java Edition 1.16, and /data get output
Most/least significant bitsUUIDMost: 475826800676128550L, UUIDLeast: -6503483008858150155LEntity data before 1.16. Still found in old worlds and old tutorials.

Reading a UUID

The hyphenated form follows the pattern xxxxxxxx-xxxx-Vxxx-Nxxx-xxxxxxxxxxxx:

  • V, the first digit of the third group, is the version. 4 means randomly generated, used for Java Edition accounts. 3 means generated from a name, used for offline-mode players.
  • N, the first digit of the fourth group, is the variant. For these UUIDs it is 8, 9, a or b.

In Notch’s UUID, 4726 shows version 4 and a5be shows the variant.

Converting between forms

  • Hyphenated ↔ plain: add or remove hyphens after the 8th, 12th, 16th and 20th hexadecimal digit.
  • Plain → int array: split the 32 digits into four groups of 8. Read each group as a 32-bit signed integer: values of 80000000 and above become negative.
  • Plain → most/least: split into two groups of 16 digits and read each as a 64-bit signed integer.

Uppercase and lowercase hex digits mean the same thing, but Minecraft writes them in lowercase.

Offline-mode UUIDs

A server with online-mode=false calculates a UUID from the player’s name: an MD5 hash of the text OfflinePlayer: followed by the exact name, with the version set to 3. The same method in Java code is UUID.nameUUIDFromBytes.

NameOffline-mode UUID
Notchb50ad385-829d-3141-a216-7e7d7539ba7f
notch42653081-a90e-3475-b3d6-3550cdb43f8e

The capitalisation changes the result, and neither matches the account UUID. The UUID Lookup shows both kinds for any name.

Bedrock Edition

Bedrock Edition identifies accounts by Xbox user ID (XUID), a number rather than a UUID. Java UUID lookups don’t apply to Bedrock players.