What makes UUID v5 different from UUID v4?

UUID v4 is randomly generated and different every time. UUID v5 is deterministic — the same namespace and name always produce the same UUID, making it reproducible and collision-resistant within a namespace.

Which namespace should I use?

Use the DNS namespace for domain names, URL for web addresses, OID for ISO object identifiers, and X.500 for distinguished names. For custom use cases, you can enter any valid UUID as a custom namespace.

Is UUID v5 cryptographically secure?

No. UUID v5 uses SHA-1 for determinism, not security. Do not use it as a secret token or password. For unpredictable identifiers, use UUID v4 instead.

Can two different inputs produce the same UUID v5?

Theoretically yes (SHA-1 collision), but in practice collisions are astronomically rare. Different namespaces with the same name will produce different UUIDs.

Does this tool send my data anywhere?

No. All computation happens in your browser using the Web Crypto API. Nothing is sent to any server.

What RFC defines UUID v5?

RFC 4122, Section 4.3 defines the algorithm for name-based UUIDs using SHA-1 (version 5).

UUID v5 Generator

Name: UUID v5 Generator
Availability: InStock
Author: Nham Vu

Generate deterministic UUID v5 identifiers from a namespace UUID and a name string using SHA-1 hashing per RFC 4122.

Namespace

Name String

Any UTF-8 string — a domain, URL, path, or arbitrary identifier.

Bulk mode

Generated UUID v5

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Enter a name and click Generate.

Copied!

Summary

Generate deterministic UUID v5 identifiers from a namespace UUID and a name string using SHA-1 hashing per RFC 4122.

How it works

Choose a standard namespace (DNS, URL, OID, X.500) or enter a custom namespace UUID.
Type the name string you want to hash into the namespace.
The tool concatenates the namespace UUID bytes and the name UTF-8 bytes, then computes SHA-1.
The first 16 bytes of the SHA-1 digest are taken and the version (5) and variant bits are set.
The resulting 128-bit value is formatted as a standard 8-4-4-4-12 UUID string.
Click "Copy UUID" to copy the result to your clipboard.

Use cases

Generate stable IDs for DNS hostnames that are always the same given the same input.
Create reproducible UUIDs for database seed data across environments.
Assign deterministic identifiers to REST resources without storing a mapping table.
Namespace URL identifiers for RDF/Linked Data graphs.
Generate test fixture IDs that remain stable across test runs.
Build content-addressable references for documents or assets.

Frequently Asked Questions

Last updated: 2026-06-09 · Reviewed by Nham Vu