UUID / GUID Generator
Generate RFC 4122 version 4 UUIDs in bulk, ready to copy as plain text, JSON, SQL or CSV.
Version 4, and why it matters
There are several UUID versions in RFC 4122. Version 1 embeds the machine's MAC address and a timestamp, which leaks when and where an identifier was created and is why it has fallen out of favour for public-facing systems. Version 4 is fully random: 122 random bits, with the version and variant nibbles set, giving 5.3 x 1036 possible values. This generator produces version 4 only.
Use it as a database key, not as a secret
A v4 UUID is unguessable in practice, but it is not a cryptographic token and should not replace a session identifier or an API key. It is excellent as a primary key when you do not want to expose sequential row counts, and as an idempotency key for webhooks and message queues.
Random UUIDs versus sequential integers
- Pro - no information leak about volume or growth rate, safe to generate client-side, no coordination needed between services.
- Con - random keys fragment B-tree indexes, so insert-heavy tables can slow down. Where write volume matters, store the UUID and keep a monotonic ordering column as well.
Frequently asked questions
Is this a version 1 or version 4 UUID?
Version 4. The generator sets the version and variant bits correctly, so the output passes RFC 4122 validation.
Can two generated UUIDs collide?
Not in any practical sense: 122 random bits mean you would need billions of identifiers per second for decades to approach a meaningful collision probability.
Can I use a UUID as a password reset token?
No. Use a purpose-built random token. UUIDs are identifiers, not secrets.
What is the difference between a UUID and a GUID?
Nothing functional. GUID is Microsoft's name for the same format.
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