UUID Generator
Generate version 4 random UUIDs.
About UUID v4
UUID v4 identifiers are randomly generated 128-bit values formatted as 32 hex digits in the pattern 8-4-4-4-12. They are statistically unique — the probability of a collision is negligibly small. Uses the browser's cryptographic random number generator.
FAQ
- Are these cryptographically secure?
- Yes. Generated using crypto.randomUUID() which uses the browser's CSPRNG.
- What's the difference between formats?
- Standard is lowercase with hyphens (RFC 4122). UPPER is the same in uppercase. No-hyphens removes the hyphens for use in contexts that don't allow them.
- What are UUIDs used for?
- Database primary keys, session IDs, file names, distributed systems identifiers, and anywhere a unique ID is needed without a central authority.
ABOUT THIS TOOL
Click once to generate a randomly generated UUID (version 4), or generate multiple at a time in bulk. A v4 UUID is 128 bits, with 122 bits coming from a random or pseudo-random source and the rest fixed to mark the version and variant per RFC 4122, giving a chance of collision so low it's treated as effectively zero even across billions of IDs. UUIDs are used as unique identifiers for database records, sessions, files, and anywhere a collision-free ID is needed without coordinating with a central counter. Generation happens locally using the browser's cryptographic random number generator, so no ID is ever sent anywhere before you use it.
HOW TO USE
- Click "Generate" to produce a single UUID v4.
- Set the quantity if you need a batch, then generate multiple at once.
- Choose formatting options like uppercase/lowercase or with/without hyphens, if offered.
- Copy a single UUID or copy the whole list at once.
- Paste the UUID(s) into your database seed script, code, or config file.
- Regenerate anytime — every click produces fresh, independent values.
COMMON USE CASES
- A backend developer seeds a test database with hundreds of fake primary keys before running integration tests.
- A frontend developer needs a unique "key" prop for a list of dynamically rendered React components.
- A DevOps engineer generates a unique idempotency key to include in an API request header.
- Someone designing a distributed system needs IDs that multiple services can generate independently without a shared counter.
- A QA engineer creates mock user IDs for a batch of test accounts.
TIPS & COMMON MISTAKES
- UUID v4 is random, not sequential — don't rely on generated UUIDs to sort by creation time; use v7-style timestamp-based UUIDs or a separate timestamp column if ordering matters.
- Standard UUID format is 36 characters including 4 hyphens (8-4-4-4-12 hex digits); some systems expect no hyphens, so check formatting before pasting into a strict field.
- A v4 UUID isn't cryptographically meant to be a secret — while collisions are astronomically unlikely, don't rely on a raw UUID as your only defense for something like a password reset token.
- If you need reproducible IDs for testing, generate them once and hardcode them in fixtures rather than regenerating on every test run.
MORE QUESTIONS
- How likely is a UUID v4 collision?
- With 122 random bits, you'd need to generate roughly 2.71 quintillion UUIDs before there's a 50% chance of a single collision, so for virtually all practical applications it's treated as impossible.
- Is a UUID the same as a GUID?
- Functionally yes — GUID is Microsoft's name for the same 128-bit identifier concept, and UUID is the more general RFC 4122 term used elsewhere.
- Why does the UUID always have specific version digits?
- In a v4 UUID, the 13th hex digit is always "4" to mark the version, and the first digit of the 4th group is always 8, 9, a, or b to mark the variant, per the RFC 4122 spec.
- Can I use a UUID as a database primary key?
- Yes, though UUIDs are larger than integers (16 bytes vs 4-8) and their randomness can hurt index locality in some databases, which is why sequential variants like UUIDv7 are gaining popularity for that use case.