Online UUID v4 Generator

How to generate a v4 UUID

Each identifier is made up of 16 bytes obtained through the random source browser cryptography. Then the bits that indicate version 4 are set and the standard variant. The result uses 32 hexadecimal digits grouped with hyphens:

xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx

The first digit of the fourth group is 8, 9, a or b. Those positions are not random: they identify the version and variant of a valid UUID.

UUID, GUID and uniqueness

UUID is the name defined by the standard; GUID is a term widely used in the Microsoft ecosystem for identifiers with the same usual format. A UUID v4 does not query a central registry. Its random space is so large that Collisions are extremely unlikely when using a safe source, but there is no absolute mathematical guarantee of uniqueness.

If your system needs to prevent any duplication, also apply a unique constraint on the place where you store the identifiers and again try in a collision.

Common uses

• Identifiers of records that are created without central coordination.
• Test data, fixtures and API examples.
• Correlation keys for events or requests.
• Opaque names when they should not reveal an incremental sequence.

A UUID is not a password, signature, or access token. Although this tool uses cryptographic randomness, format exposes some bits fixed and should not replace a mechanism designed for authentication.

Quantity, format and copy

You can generate between 1 and 100 values ​​in one operation. Each click creates a batch new and the copy button retains one identifier per line. letters are used lowercase hexadecimal and no curly braces or prefixes are added.

To obtain the fingerprint of a text use the generator SHA-256. To transform bytes or text into another representation, see Base64.

Privacy and Compatibility

Generation happens entirely in this tab using Web Crypto. The UUIDs are not saved, are not sent to Tools in a Tab, and are lost on reload. A old browser or a context that does not allow safe randomness will show a error instead of resorting to Math.random().

Frequently asked questions

Can I regenerate exactly the same batch?

Not intentionally. Each operation requests new random bytes and does not use a reproducible seed.

Sort UUIDs by date?

No. Version 4 is random. If you need temporary order, study UUID v7 and the specific guarantees of your platform.

Would capitalization change the identifier?

No. Hexadecimal comparison is usually case insensitive, but generates the canonical representation in lowercase.

Technical reference

The current version, variant, and textual format are defined in RFC 9562.