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Generate random UUID v4 identifiers for databases, APIs, and development.
A UUID (Universally Unique Identifier) is a 128-bit identifier guaranteed to be unique across space and time. UUID v4, the most common version, is generated from random numbers and is widely used as database primary keys, session tokens, and API request IDs.
c53f5ef3-dcbc-43b4-8e1f-00a5e200a594UUID v4 follows a standard 8-4-4-4-12 format with 36 characters (32 hex digits + 4 hyphens):
xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx| Version | Generation Method |
|---|---|
| v1 | Timestamp + MAC address |
| v3 | MD5 hash of namespace + name |
| v4 | Random (this generator) |
| v5 | SHA-1 hash of namespace + name |
| v7 | Unix timestamp + random (sortable) |
Formula
xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx4 = Fixed digit indicating UUID version 4 (random)
y = One of 8, 9, a, or b — encodes the RFC 4122 variant bits
x = Random hexadecimal digit (0–f), 122 bits of entropy total
Worked Example
Example: generating a UUID v4
Did you know? The probability of generating a duplicate UUID v4 is roughly 1 in 5.3 undecillion (5.3 × 10³⁶). At one billion UUIDs generated per second, you'd expect a collision after about 85 years.
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