UUID Generator (v4 & v7)

What is a UUID?

A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit value written as 32 hexadecimal digits in the pattern xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. The point of a UUID is that you can generate one anywhere — on any machine, with no central coordination — and be confident it won't collide with any other. That makes UUIDs ideal for database primary keys, request IDs, idempotency keys and distributed systems.

v4 vs v7 — which should you use?

• v4 (random) — 122 bits of randomness. The universal default: unpredictable and simple. The downside is that random keys are scattered, so inserting them as a database primary key can fragment the index.
• v7 (time-ordered) — embeds a millisecond timestamp in the high bits, so v7 UUIDs sort roughly in creation order. This keeps database indexes compact and improves insert performance, while still being globally unique. It's the modern choice for new primary keys (standardised in RFC 9562).

Rule of thumb: use v7 for database keys where insert ordering matters, and v4 when you want a pure random identifier with no embedded timestamp.

Are these UUIDs secure / unique?

They are generated with your browser's cryptographic random source, so the random portions are unpredictable and the chance of a collision is astronomically small — you would need to generate billions of UUIDs before a duplicate became remotely likely. Note, however, that a v4 UUID is not a secret: it's unique, not unguessable in the security sense for short ranges. For tokens that must resist guessing, use a dedicated API key with explicit entropy instead.

Common uses

• Primary keys that can be generated client-side before an insert.
• Correlation/request IDs for tracing a call across microservices.
• Idempotency keys so retried API requests aren't processed twice.
• Stable identifiers for files, events or messages in a queue.

Bulk generation

Need a batch for seeding a database or a test fixture? Set the count and generate up to 1,000 at once, then copy them all. Every value is produced locally in your browser — nothing is sent to a server.