UUID Generator
Generate UUIDs one at a time or a hundred at once, in version 4 or the newer time-ordered version 7. Paste one you were handed and it tells you the version, the variant, and (for a v7) the moment it was created.
Version 4 · random
Inspect a UUID
Paste one you were given, with or without dashes or braces, to read its version, variant, and for a v7 the moment it was created.
Common questions
- What is the difference between UUID v4 and v7?
- A v4 is 122 random bits and carries no information. A v7 puts a millisecond timestamp in the first 48 bits and fills the rest with randomness, so v7 values sort chronologically as plain strings. That is the practical difference: v4 keys scatter across a database index while v7 keys append, which keeps the index compact and inserts fast.
- Are these random enough to use as secrets?
- They come from crypto.getRandomValues, the browser's cryptographically secure generator, not from Math.random. That said, a v7 deliberately reveals when it was made, so prefer v4 if the value must not leak timing. For an authentication token, use a purpose-built secret rather than any UUID.
- What are the odds of a collision?
- For version 4, negligible at any scale you will meet. You would need to generate around 2.7 × 10^18 of them before a 50% chance of a single duplicate. A v7 is stronger still in practice, because two values only compete if they were created in the same millisecond.
- What is the nil UUID for?
- It is all zero bits, and it stands for "no value" in a column that cannot be null. The max UUID is its opposite, all one bits, and is mainly used as an upper bound in range queries.
- What does the variant field mean?
- Two or three bits that say which UUID specification the value follows. Almost everything you will meet is the RFC 9562 variant. The legacy NCS and Microsoft variants appear in old data, and the inspector names them rather than silently treating them as modern UUIDs.
- Is anything generated on a server?
- No. The values are created in your browser and never transmitted, which matters if you are generating identifiers that will end up in production data.
Exact, and cryptographically random. The browser generates the values, not a seeded pseudo-random source.