Click Generate to create one or more version 4 UUIDs. They're produced entirely in your browser using its cryptographically secure random generator — click any result to copy it, or copy them all at once.
What is a UUID?
A UUID (Universally Unique Identifier), sometimes called a GUID, is a 128-bit value written as 32 hexadecimal digits in the familiar 8-4-4-4-12 pattern, like f47ac10b-58cc-4372-a567-0e02b2c3d479. Its whole purpose is to let different systems generate identifiers independently and still be confident they'll never collide — no central authority or database lookup required.
Version 4 UUIDs (what this tool makes) are almost entirely random: 122 of the 128 bits are random, with a few fixed bits marking the version and variant. You can spot a v4 UUID because the 13th hex digit is always 4.
When and why you'd use it
- Database keys — primary keys that can be created on the client or across shards without coordinating with a central counter.
- Distributed systems — request IDs, message IDs, and trace IDs that stay unique across many servers.
- Files and resources — unique filenames or object keys that won't clash.
- Idempotency keys — safely retrying an API call without creating duplicates.
Worked examples
4 starting the third group, marking version 4.Frequently asked questions
Could two UUIDs ever be the same?
In practice, no. With 122 random bits there are about 5×1036 possible v4 UUIDs. You would need to generate billions per second for many years before a single collision became even remotely likely.
What's the difference between v1 and v4?
Version 1 is based on the time and the machine's network address (so it can leak those). Version 4 is random, which is why it's the common default when you just need a unique, opaque ID.
Are these generated randomly and privately?
Yes. They're created locally with crypto.randomUUID(), which uses the browser's cryptographically secure random source. Nothing is sent to a server, and no list is stored.
Can I use a UUID as a database primary key?
Yes, and it's common. One trade-off: random v4 UUIDs aren't ordered, which can fragment some database indexes. If insert-order matters for performance, look at time-ordered schemes (like UUIDv7).