UUID Generator
Generate random version 4 UUIDs individually or in bulk.
Generate version 4 UUIDs — the random kind used as unique identifiers for records, files, sessions, and API keys. Create one at a time or a batch, then copy the lot. They're produced with your browser's cryptographic random source.
What a UUID is
A UUID (universally unique identifier), also called a GUID, is a 128-bit value written as 32 hexadecimal digits in five dash-separated groups. Version 4 UUIDs are almost entirely random, which makes accidental collisions vanishingly unlikely — you can generate them independently on many machines without coordination and still expect every one to be unique.
Where to use them
UUIDs are ideal as database primary keys when you can't rely on a central counter, as filenames that won't clash, as idempotency keys for API requests, and as opaque session or object identifiers that reveal nothing about how many records exist. Because they don't leak sequence information, they're friendlier to security and to distributed systems than incrementing integers.
UUIDs versus auto-increment IDs
Sequential integer IDs are compact and sort naturally, but they leak information — a competitor can guess how many orders you've had, and two systems generating IDs independently will collide. UUIDs solve both: they can be created anywhere without a central authority, and they reveal nothing about volume or sequence. The trade-off is size (16 bytes versus a few) and that they don't sort by creation time. For distributed systems, public-facing identifiers, and merge-friendly data, that trade is usually worth it.
When to use a UUID instead of a counter
A UUID is a 128-bit identifier designed to be unique without any central authority handing out numbers. That property is its whole reason for existing. A simple auto-incrementing counter works fine inside one database, but the moment you have several services, offline clients, or systems that must merge later, coordinating a single counter becomes a bottleneck or a conflict. UUIDs sidestep the problem: any machine can mint one at any time and the odds of a collision are so remote they can be treated as zero for practical purposes.
The trade-off is readability and size. A UUID is far longer than "1042" and impossible to memorise or dictate over the phone, and as a database key it takes more space and can fragment indexes if generated randomly. Version 4 UUIDs — the random kind this tool produces — are the common default for application IDs, API keys, and idempotency tokens. Reach for them when independence and uniqueness matter more than compactness, and stick with a plain sequence when you have a single source of truth and value short, human-friendly numbers.
Frequently asked questions
Are these UUIDs unique?
Version 4 UUIDs are random 128-bit values. The chance of two colliding is astronomically small, so for practical purposes each one is unique.
Are they generated securely?
Yes. They use the browser's cryptographic random number generator (crypto.randomUUID or crypto.getRandomValues), entirely on your device.
Can I generate many at once?
Yes. Set the count and generate up to a thousand at a time, then copy them all.
What's the difference between a UUID and a GUID?
None in practice. GUID is Microsoft's name for the same 128-bit identifier standard. The formats are interchangeable.
Can I use a UUID as a database primary key?
Yes, and many teams do for distributed or public-facing systems. Be aware that random v4 UUIDs don't cluster by insertion time, which can affect index performance on some databases.
Can two random UUIDs ever collide?
In theory yes, but a version 4 UUID has 122 random bits, so the probability is vanishingly small — you can generate billions without any realistic chance of a clash.
Last updated: 2026-01-15