UUID v1 vs v4 vs v7 — Which Version to Choose?
RFC 4122 defines several UUID versions. The three you'll see most often are v1 (time-based), v4 (random), and v7 (time-ordered). Here's a quick comparison to help you choose.
Version 1 — Time-Based
Version 1 UUIDs encode a timestamp and a node (often derived from MAC in servers; in browsers it's random). They're unique and roughly time-ordered. Use v1 when you need time ordering or legacy compatibility. Drawbacks: timestamp and node can leak information; ordering is only approximate.
Version 4 — Random
Version 4 UUIDs are generated from random data. They're the most common choice for new applications: session IDs, record IDs, tokens. No time or machine component, so they're safe across distributed systems. Use v4 when you just need a unique ID and will store it. Our generator and API default to v4.
Version 7 — Time-Ordered
Version 7 (draft RFC 9562) combines a millisecond timestamp with random data. UUIDs are sortable by creation time, which helps database indexes and time-based queries. Use v7 when you want both uniqueness and natural time order without v1's complexity.
Quick Comparison
- v1: Time-based, legacy, approximate ordering.
- v4: Random, no ordering, safest default for new IDs.
- v7: Time-ordered, good for indexes and sorting by creation.
Need many at once? Use our bulk generator. To check a string, use our validator.