About this tool
UUIDs (Universally Unique Identifiers) are 128-bit values used as unique IDs for database rows, API resources, and distributed systems, chosen so that two independently generated IDs are astronomically unlikely to collide. This tool generates RFC 4122 version 4 UUIDs — the fully random variant — using your browser's cryptographic random number generator.
How to use it
- 1Set how many UUIDs you want to generate.
- 2Toggle uppercase and hyphens to match the format your system expects.
- 3Click "Generate" for a new batch, or "Copy all" to copy every UUID, one per line.
Common mistakes to avoid
- Assuming UUIDs are sequential or sortable — version 4 UUIDs are fully random and carry no ordering information.
- Stripping hyphens without checking whether the target system expects the standard 8-4-4-4-12 format.
- Using a UUID as a security token — UUIDs are unique, but not all generators are cryptographically unpredictable (this one is, via the Web Crypto API).
Use cases
- Generating primary keys or reference IDs for a database schema.
- Creating placeholder IDs while prototyping an API.
- Producing unique identifiers for test fixtures or seed data.
Frequently asked questions
Are these UUIDs guaranteed to be unique?
They're generated using crypto.randomUUID(), which follows the RFC 4122 version 4 spec. Collisions are theoretically possible but practically negligible — you'd need to generate billions of UUIDs before a collision became statistically likely.
What's the difference between a UUID and a GUID?
They're effectively the same concept — GUID (Globally Unique Identifier) is Microsoft's term for the same 128-bit identifier format defined by the UUID standard.