UUID v7 Sorts by Creation Time While UUID v4 Stays Random

This technical guide compares UUID versions 4 and 7 to help developers choose the right identifier. Version 7 embeds a millisecond Unix timestamp in its first 48 bits, so values sort chronologically, making it suitable for database primary keys and ordered event logs. Version 4 is almost entirely random, which keeps it unordered and avoids revealing when it was created, so it fits publicly exposed identifiers. The article explains the 8-4-4-4-12 format and how the version and variant digits mark each UUID's type, and it notes that RFC 9562 from 2024 formally standardized versions 6 through 8. It also stresses generating UUIDs from cryptographically secure sources, such as crypto.randomUUID() or Python's uuid4(), rather than Math.random().