About this UUID generator
A UUID, also called a GUID on Windows, is a 128-bit identifier written as 32 hexadecimal digits in five groups, such as 3f2b8c1e-9d4a-4c6b-a1f0-7e2d5b8c9a01. UUIDs let databases, APIs, and distributed systems create IDs without a central counter. Version 4 is random and is what most developers need; version 1 is built from the current time, so IDs sort roughly by creation time; version 5 is built from a namespace and a name, so the same input always gives the same UUID. Random numbers come from your browser’s cryptographic generator, and nothing is sent to a server.
How to generate UUIDs
- Choose a version. Pick version 4 for random IDs, version 1 for time-based IDs, or version 5 for an ID derived from a name.
- Set the details. Enter how many UUIDs you need and choose a format. For version 5, pick a namespace and type the name.
- Press Generate UUIDs. The UUIDs appear one per line; press Copy all or Download.
- Check an existing UUID. Paste a UUID into Check a UUID and press Check UUID to see whether it is valid, its version, and for version 1 when it was created.
Frequently asked questions
Is a GUID the same as a UUID?
Yes. GUID is Microsoft’s name for the same 128-bit identifier. The braces format {…} matches how Windows and .NET usually display GUIDs.
Can two version 4 UUIDs ever be the same?
In theory, but not in practice. A version 4 UUID has 122 random bits; you would need to generate billions of UUIDs every second for many years before a duplicate became likely.
Why does version 5 give the same UUID every time?
Version 5 is a SHA-1 hash of the namespace and the name, so it is repeatable by design. For example, the DNS namespace with www.example.com always gives 2ed6657d-e927-568b-95e1-2665a8aea6a2. That is why only one v5 UUID is generated per name.
Does version 1 reveal my computer’s MAC address?
Not here. Browsers cannot read a MAC address, so the node part is random with the multicast bit set, as the UUID standard allows. The timestamp part is real, and the checker below can read it back.
Which format should I use?
The standard lowercase form with hyphens works almost everywhere. Use no hyphens for compact storage, braces for Microsoft tools, and the URN form when a spec asks for urn:uuid:.