UUID Generator
Generate v1, v4, v5 or Nil UUIDs, one at a time or up to 100 at once.
Generated UUID
d55927db-7cad-40d1-8bf1-e4d433e169aa
Generated UUIDs
Copied to clipboard.
How to use it
- Pick a version. For v5, enter a namespace and a name.
- Choose single or bulk mode. Bulk accepts 1 to 100 UUIDs.
- Pick an output format: plain, braces, quotes or comma-separated.
- Copy one UUID, or use Copy all.
A UUID has 128 bits. In v4, 6 of them mark the version and variant and 122 are random, which gives about 5.3 x 10^36 possible values.
UUID versions compared
| Version | Based on | Best for | Watch out for |
|---|---|---|---|
| v4 | 122 random bits | General IDs, database keys, session IDs | Not sortable by creation time |
| v1 | Timestamp plus node ID | IDs that roughly follow creation time | Exposes when the ID was made |
| v5 | SHA-1 of namespace and name | Stable IDs: same input, same UUID | Not random, so inputs must be unique |
| Nil | All zero bits | Marking an empty value | Never use it as a real identifier |
Frequently Asked Questions
Which UUID version should I use?
Use v4 unless you have a reason not to. It is random and fits most IDs, such as database keys and request IDs. Use v5 when the same input must always give the same UUID. Use v1 when you want IDs that roughly follow creation time.
Are the UUIDs random enough?
v4 UUIDs are made from the cryptographic random source of the uuid library, with 122 random bits. That makes accidental duplicates practically impossible.
How does v5 work?
It hashes a namespace UUID and a name with SHA-1. The same namespace and name always return the same UUID. The DNS and URL buttons fill in the standard namespaces.
What is the Nil UUID?
The all-zero UUID, 00000000-0000-0000-0000-000000000000. It stands for no value and should not be used as a real ID.
Are my inputs sent anywhere?
No. UUIDs are generated in your browser and the v5 name stays on your device.
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