What is the UUID Generator?
A version-4 UUID contains 122 random bits, giving 5.3 × 1036 possible values — collisions are practically impossible. Our UUIDs use cryptographic randomness and set the version and variant bits correctly, so they validate in every language and database.
A UUID is 128 bits written as 32 hexadecimal digits in five hyphen-separated groups of 8, 4, 4, 4 and 12 characters. In a version-4 UUID the first digit of the third group is always 4, and the first digit of the fourth group is 8, 9, a or b — those six fixed bits mark the version and variant, leaving 122 random ones. That pattern makes v4 UUIDs easy to recognise in logs. RFC 4122 has since been replaced by RFC 9562, published in 2024, which keeps version 4 unchanged.
How to use the UUID Generator
- Adjust the options above to match what you need.
- Press Generate (or hit Enter / Space) to create fresh results instantly.
- Click any result to copy it, or use Copy all.
- Download everything as CSV, JSON or TXT, or share a link with your settings.
Popular uses
- Database primary keys — globally unique IDs without a central sequence.
- Fixtures & mocks — IDs for JSON test fixtures.
- Windows / .NET — GUIDs in braces for registry keys and COM.
Why use RandNow?
- Instant & unlimited — no sign-up, no daily caps.
- Private by design — results are generated in your browser, not on our servers.
- Export-ready — copy, CSV, JSON and TXT downloads built in.
- Cryptographically random — powered by the Web Crypto API.
UUIDs as database keys
Random v4 UUIDs let any server or client create IDs without coordination, which is ideal for distributed systems and offline apps. The trade-off is index locality: because each new key lands at a random spot in a B-tree index, large tables with heavy inserts can see more page splits than with sequential integers. If that matters, consider the time-ordered version 7 defined in RFC 9562, and store UUIDs in a native 16-byte type rather than a 36-character string when your database supports it.
Where UUIDs aren’t the right tool
A UUID is designed to be unique, not secret. For password-reset tokens, session IDs or API keys, use a purpose-built token with a clearly defined amount of randomness and a reviewed security design. For fixtures, record IDs, correlation headers and file names, though, v4 UUIDs are a perfect fit, and they never reveal how many records you hold. Press Generate to create your next batch.
Frequently asked questions
What is the difference between a UUID and a GUID?
They are the same thing. GUID is Microsoft’s name for a UUID.
Can two UUIDs ever be the same?
Theoretically yes, but you’d need to generate about 2.7 quintillion v4 UUIDs for a 50% chance of a single collision.
Which version do you generate?
Version 4 (random), the most widely used version.
Are UUIDs case-sensitive?
No. The standard recommends writing them in lowercase but accepting either case on input, so 3F2A… and 3f2a… are the same UUID.
What is UUID version 7?
A newer, time-ordered format from RFC 9562 that begins with a Unix timestamp in milliseconds followed by random bits, so new IDs sort roughly in creation order. This tool generates version 4.