UUID Generator Online

A UUID is a 128-bit identifier you can generate anywhere — on any server, any device, without coordinating with a central database — and still trust to be unique. That property makes it the default choice for distributed primary keys, trace IDs that follow a request across services, and idempotency keys that let a client safely retry an operation without creating duplicates.

The version number tells you how the ID was produced. Version 4 is 122 random bits laid out as 8-4-4-4-12 hexadecimal digits, and it is what most applications want: no inputs, no ordering, just randomness with a collision probability low enough to ignore in practice. Version 1 embeds a timestamp and the machine's MAC address, so it sorts roughly by creation time but leaks where and when it was made. Versions 3 and 5 are deterministic — hash a namespace plus a name and you always get the same UUID back, useful when the same input must map to a stable ID.

How to use it

  1. Pick the version you need — v4 for general-purpose random IDs, v1 for time-ordered, v3/v5 for deterministic namespaced IDs.
  2. For v3 or v5, provide the namespace UUID and the name string to hash.
  3. Set how many UUIDs to generate if you need a batch.
  4. Copy the result into your database, config, or test fixtures.

Common use cases

Examples

A version 4 UUID

Input Version: v4, Count: 1

Output f47ac10b-58cc-4372-a567-0e02b2c3d479

The 13th digit is 4, marking the version; the rest is random. Format is 8-4-4-4-12 hex digits.

Deterministic v5 from a name

Input Version: v5, Namespace: DNS, Name: example.com

Output cfbff0d1-9375-5685-968c-48ce8b15ae17

The same namespace and name always yield this exact UUID, so it is reproducible rather than random.

Frequently asked questions

Which UUID version should I use?
Version 4 (random) for almost everything — keys, tokens, correlation IDs. Use v5 when the same input must always map to the same ID, and v1 only when you need rough time-ordering and don't mind exposing a timestamp.
Can two UUIDs ever collide?
In theory yes, in practice no. A v4 UUID has 122 random bits; you would need to generate billions per second for many years before a collision became likely.
Are UUIDs safe to use as passwords or secret tokens?
No. A v4 UUID is random but not designed as a cryptographic secret, and v1/v3/v5 are partly predictable. For secrets, use a purpose-built token generator.
Is a UUID the same as a GUID?
Yes. GUID is Microsoft's name for the same 128-bit identifier; the two terms are interchangeable.

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