UUID generator — v4 & v7

v4 or v7 — which one for your API?

v4 is 122 bits of pure randomness: unguessable, zero coordination, the default for tokens and request IDs. Its weakness is databases — random primary keys scatter inserts across the index. v7 fixes exactly that: the first 48 bits are a Unix timestamp, so IDs sort by creation time and B-tree inserts stay append-friendly, while the remaining bits stay random. Rule of thumb: external/security-sensitive identifiers → v4; database keys and anything you'll sort or paginate by → v7. Note that v7 deliberately leaks creation time — don't use it where that's sensitive.

Need a fresh UUID inside a request body? ReqPad ships {{$randomUUID}} and {{$guid}} as dynamic variables — every send gets a new one, on your phone. See also the JWT decoder.