Version 8: Custom


Version 8, custom UUIDs are a new format of UUID, proposed in an Internet-Draft under review at the IETF. While the draft is still going through the IETF process, the version 8 format is not expected to change in any way that breaks compatibility.

Version 8 UUIDs allow applications to create custom UUIDs in an RFC-compatible way. The only requirement is the version and variant bits must be set according to the UUID specification. The bytes provided may contain any value according to your application’s needs. Be aware, however, that other applications may not understand the semantics of the value.


The bytes should be a 16-byte octet string, an open blob of data that you may fill with 128 bits of information. However, bits 48 through 51 will be replaced with the UUID version field, and bits 64 and 65 will be replaced with the UUID variant. You must not rely on these bits for your application needs.

Generate a version 8, custom UUID
use Ramsey\Uuid\Uuid;

$uuid = Uuid::uuid8("\x00\x11\x22\x33\x44\x55\x66\x77\x88\x99\xaa\xbb\xcc\xdd\xee\xff");

    "UUID: %s\nVersion: %d\n",

This will generate a version 8 UUID and print out its string representation. It will look something like this:

UUID: 00112233-4455-8677-8899-aabbccddeeff
Version: 8