5.8. UUID Version 8

UUIDv8 provides an RFC-compatible format for experimental or vendor-specific use cases. The only requirement is that the variant and version bits MUST be set as defined in Sections 4.1 and 4.2. UUIDv8's uniqueness will be implementation-specific and MUST NOT be assumed.

The only explicitly defined bits are those of the version and variant fields, leaving 122 bits for implementation-specific UUIDs. To be clear, UUIDv8 is not a replacement for UUIDv4 (Section 5.4) where all 122 extra bits are filled with random data.

Some example situations in which UUIDv8 usage could occur:

An implementation would like to embed extra information within the UUID other than what is defined in this document.
An implementation has other application and/or language restrictions that inhibit the use of one of the current UUIDs.

Appendix B provides two illustrative examples of custom UUIDv8 algorithms to address two example scenarios.

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           custom_a                            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          custom_a             |  ver  |       custom_b        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|var|                       custom_c                            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           custom_c                            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 12: UUIDv8 Field and Bit Layout

Field Definitions:

custom_a: The first 48 bits of the layout that can be filled as an implementation sees fit. Occupies bits 0 through 47 (octets 0-5).

ver: The 4-bit version field as defined by Section 4.2, set to 0b1000 (8). Occupies bits 48 through 51 of octet 6.

custom_b: 12 more bits of the layout that can be filled as an implementation sees fit. Occupies bits 52 through 63 (octets 6-7).

var: The 2-bit variant field as defined by Section 4.1, set to 0b10. Occupies bits 64 and 65 of octet 8.

custom_c: The final 62 bits of the layout immediately following the var field to be filled as an implementation sees fit. Occupies bits 66 through 127 (octets 8-15).

5.8. UUID Version 8​

5.8. UUID Version 8