How do I generate UUID v5 from a string?

Select V5, choose the standard DNS, URL, OID or X.500 namespace, or enter a custom namespace UUID, then type the name and press Generate UUID v5. DNS with python.org produces 886313e1-3b8a-5372-9b90-0c9aee199e5d. The namespace bytes and exact UTF-8 name are hashed with SHA-1, as required by UUID v5, then version and variant bits are set. Case, spaces and Unicode normalization change the result. An empty name is allowed, and an incomplete Unicode surrogate is refused. The name is not saved or uploaded.

Why is my UUID v5 different from another implementation?

Check the namespace UUID and the exact UTF-8 name, including case, leading or trailing whitespace and composed versus decomposed Unicode. This page does not lowercase domains, normalize URLs or Unicode, trim names or append a newline. Namespaces and names must match byte for byte.

What are the odds of a UUID collision?

For independent uniformly random v4 values there are 2^122 possible random-bit combinations. The birthday approximation reaches a 50% chance of a duplicate near 2.7 × 10^18 generated values; no finite batch proves global uniqueness. V7 has a different timestamp/counter/random layout and depends on clock behavior, so the v4 estimate does not describe it. V5 deliberately repeats for the same namespace and name and uses SHA-1, whose collision resistance is not suitable for security-sensitive proof of identity.

Are UUIDs passwords, API secrets or authentication tokens?

Use a purpose-built password or secret generator for those jobs. V4 draws secure randomness, but a UUID is an identifier and does not implement an application’s token lifecycle. V7 exposes its timestamp, v5 is predictable from its inputs, and Nil and Max are fixed constants.

UUID v5 Generator

Create a deterministic name-based UUID v5. This page opens V5 and the standard DNS namespace. Choose a namespace, type the exact name and generate one result. Repeating the same namespace and name repeats the UUID.

Version 5 · namespace and nameReady

Version

Format

Namespace and exact name

Namespace UUIDName (exact UTF-8 text)

The same namespace and exact name produce the same UUID. Case, whitespace and Unicode normalization matter; an empty name is allowed. The name stays in this tab and is never saved.

Validate and inspect a UUID

Check the representation, version and variant. For an RFC v7, read the embedded timestamp. This cannot prove uniqueness, origin or authenticity.

UUID

Formatting, count, version and a valid namespace can be remembered on this device. Names, generated UUIDs and inspection input are not saved. Page presets preserve remembered choices until you explicitly change each setting.

Common questions

How do I generate UUID v5 from a string?: Select V5, choose the standard DNS, URL, OID or X.500 namespace, or enter a custom namespace UUID, then type the name and press Generate UUID v5. DNS with python.org produces 886313e1-3b8a-5372-9b90-0c9aee199e5d. The namespace bytes and exact UTF-8 name are hashed with SHA-1, as required by UUID v5, then version and variant bits are set. Case, spaces and Unicode normalization change the result. An empty name is allowed, and an incomplete Unicode surrogate is refused. The name is not saved or uploaded.
Why is my UUID v5 different from another implementation?: Check the namespace UUID and the exact UTF-8 name, including case, leading or trailing whitespace and composed versus decomposed Unicode. This page does not lowercase domains, normalize URLs or Unicode, trim names or append a newline. Namespaces and names must match byte for byte.
What are the odds of a UUID collision?: For independent uniformly random v4 values there are 2^122 possible random-bit combinations. The birthday approximation reaches a 50% chance of a duplicate near 2.7 × 10^18 generated values; no finite batch proves global uniqueness. V7 has a different timestamp/counter/random layout and depends on clock behavior, so the v4 estimate does not describe it. V5 deliberately repeats for the same namespace and name and uses SHA-1, whose collision resistance is not suitable for security-sensitive proof of identity.
Are UUIDs passwords, API secrets or authentication tokens?: Use a purpose-built password or secret generator for those jobs. V4 draws secure randomness, but a UUID is an identifier and does not implement an application’s token lifecycle. V7 exposes its timestamp, v5 is predictable from its inputs, and Nil and Max are fixed constants.

UUID v4 uses secure browser randomness. UUID v7 includes the device-clock timestamp, a counter and random bits; clock rollback and other tabs are outside its ordering guarantee. UUID v5 follows the SHA-1 namespace/name construction and is deterministic, not secret. Inspection checks representation and layout, not uniqueness or authenticity.