UUID version 5 is a name-based UUID. Given the same namespace and name, it always produces the same UUID by hashing them with SHA-1. This makes v5 perfect when you need reproducible identifiers derived from existing data.
Enter a namespace UUID and a name below and this tool will generate the corresponding v5 UUID in your browser. The same inputs will always yield the same output.
What makes UUID v5 deterministic?
Rather than using randomness, v5 concatenates a namespace UUID with a name string and runs the result through SHA-1, then formats 128 bits of the digest as a UUID. Identical inputs always produce identical UUIDs, with no central coordination required.
Standard namespaces exist for DNS, URLs, OIDs, and X.500 names, but you can supply any valid UUID as your own namespace to scope your identifiers.
When to use UUID v5
Use v5 when you want a stable UUID for a real-world entity — for example, deriving a consistent ID for a URL, a username, or a file path — so that the same entity always maps to the same identifier across services and runs.
If you instead need unguessable random IDs, use v4; if you need time-ordered IDs, use v7. UUID v3 is similar to v5 but uses MD5; v5’s SHA-1 basis is generally preferred.
Frequently asked questions
- Will the same name always produce the same UUID v5?
- Yes. As long as the namespace and name are identical, v5 always produces the same UUID, which is the entire point of name-based UUIDs.
- What namespace should I use?
- Use one of the standard namespaces (DNS, URL, OID, X.500) when appropriate, or generate your own namespace UUID to keep your identifiers isolated from others.
- What is the difference between UUID v3 and v5?
- Both are name-based and deterministic. v3 hashes with MD5 while v5 uses SHA-1. v5 is generally recommended over v3.