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Although the specification for UUIDv7 is still in draft, the UUIDv7 algorithm has been relatively stable as it progresses to completion. Version 7 UUIDs can be very useful, because they are lexographically sortable, which can improve e.g: database index locality. See section 6.10 of the draft specification for further explanation: https://datatracker.ietf.org/doc/draft-ietf-uuidrev-rfc4122bis/ The specification allows up to 12 bits of extra timestamp precision, to make UUID generation closer to monotonically increasing. This provides between 1ms and ~240ns of timestamp precision. At the cost of some code complexity and a small performance penalty, a kwarg may specify any arbitrary precision between 0 and 12 extra bits. Any stronger guarantees of monotonicity have considerably larger tradeoffs, so nothing more is implemented. This limitation is documented. Ruby issue: https://bugs.ruby-lang.org/issues/19735 https://github.com/ruby/securerandom/commit/34ed1a2ec3