How this UUID generator works
A UUID is a 128-bit number designed so that anyone can mint one independently and still be confident it won't clash with one created somewhere else. It is normally written as 32 hexadecimal characters split into five groups — 8-4-4-4-12 — separated by hyphens. This tool produces version 4 UUIDs, the variety that is generated from random data rather than from a timestamp or MAC address.
When you press Generate, the page asks your browser's cryptographic random source for fresh bytes — via crypto.randomUUID() where it exists, or a crypto.getRandomValues fallback otherwise. Two specific positions are then fixed: the version nibble is set to 4, and the top bits of the variant byte are set to 10. Everything else stays random, which is what makes each value effectively unique.
550e8400-e29b-41d4-a716-446655440000. The third group is 41d4 — its first digit, 4, is the version, confirming this is a version-4 UUID. The fourth group is a716 — its first digit, a (binary 1010), starts with 10, which is the standard variant. The remaining 122 digits are random.The format of a UUID
| Segment | Example | Hex digits | Meaning |
|---|---|---|---|
| 1 — time_low | 550e8400 | 8 | Random bits |
| 2 — time_mid | e29b | 4 | Random bits |
| 3 — time_hi_and_version | 41d4 | 4 | First digit is the version (4) |
| 4 — clock_seq | a716 | 4 | First digit encodes the variant (8, 9, a or b) |
| 5 — node | 446655440000 | 12 | Random bits |
Reference note: this tool follows RFC 4122 / RFC 9562 for version-4 UUIDs. All randomness comes from the Web Crypto API in your own browser; nothing is generated or stored on a server.
Frequently asked questions
- What is a UUID?
- A UUID (universally unique identifier) is a 128-bit value used to label information so it can be identified without a central authority. It is usually written as 32 hexadecimal digits in five hyphen-separated groups, for example 550e8400-e29b-41d4-a716-446655440000.
- What is a version 4 UUID?
- A version-4 UUID is generated almost entirely from random numbers. Of its 128 bits, 122 are random; the remaining bits encode the version (4) and the variant. This generator uses your browser's cryptographic random source to produce them.
- Are these UUIDs unique and safe to use?
- For practical purposes, yes. With 122 random bits the chance of two version-4 UUIDs colliding is astronomically low — you would need to generate billions of UUIDs before a collision became likely. They are well suited to database keys, file names and request IDs.
- How do I generate multiple UUIDs?
- Set the "How many" field to any number from 1 to 1000 and press Generate. The UUIDs appear one per line, and you can switch on the comma-separated or wrap-in-quotes options to paste them straight into code.
- What's the difference between a UUID and a GUID?
- None in practice — they are the same thing. GUID (globally unique identifier) is the name Microsoft uses for the same 128-bit standard that the rest of the industry calls a UUID. A v4 UUID and a v4 GUID are identical in format.
- Are these generated on a server?
- No. Every UUID is generated locally in your browser using the Web Crypto API. Nothing is sent to a server, so the values you create are never transmitted or logged anywhere.