Canonical format
- Input
- crypto.randomUUID()
- Expected output
- 550e8400-e29b-41d4-a716-446655440000
Always 36 characters with 4 hyphens. The 13th hex is always "4" (version) and the 17th is "8", "9", "a" or "b" (RFC 4122 variant).
uuid v4 generator online
Online UUID v4 generator
UUID v4 is the most popular format for unique identifiers: 122 bits of cryptographically secure randomness, defined by RFC 9562. It is ideal for record IDs, sessions, log correlation and any context where collisions must be practically impossible.
What makes UUID v4 secure?
- UUID v4 uses 122 random bits from a CSPRNG (Cryptographically Secure Pseudo-Random Number Generator). With 2¹²² possible values (~5.3×10³⁶), the probability of a collision between two independently generated UUIDs is astronomically small.
- The browser's native crypto.randomUUID() API uses the OS CSPRNG, ensuring adequate entropy quality. No data is sent to any server.
UUID v4 examples
Database ID
- Input
- INSERT INTO users (id, ...) VALUES (?, ...)
- Expected output
- 6ba7b810-9dad-11d1-80b4-00c04fd430c8
PostgreSQL has a native UUID type; MySQL stores it as CHAR(36) or BINARY(16).
Full tool FAQ
A UUID v4 is a 128-bit unique identifier generated with random bits, except for the 4 version bits (position 13) and 2 variant bits (position 19). The format is xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where y is 8, 9, a or b.
Frequently asked questions
Can UUID v4 collide?
In theory, yes — but the probability is so low it is considered negligible for virtually all practical cases. You would need to generate one billion UUIDs per second for 85 years to have a 50% chance of a collision. For most systems, that is safe enough.
Does this page replace official or professional review?
No. It helps explain the scenario and use the tool more safely, but real decisions should consider official sources, full context and qualified guidance when needed.