UUID Generator
Generates cryptographically secure UUIDs — random v4 or time-ordered v7. Uses the browser's Web Crypto API; no value is sent to a server.
Generated UUIDs
Press "Generate".
Count must be between 1 and 100.
Frequently Asked Questions
What is a UUID v4?
A UUID v4 is a 128-bit identifier with 122 randomly generated bits. It is unique without a central authority and is ideal for database primary keys, session IDs and file names. The collision probability is negligible in practice.
What is the difference between v4 and v7?
v4 is fully random; the generated values are not ordered. v7 carries a Unix millisecond timestamp in its first 48 bits — it is time-ordered. That makes v7 far more efficient as a database primary key: index fragmentation drops and inserts stay sequential.
Are these UUIDs generated securely?
Yes. The randomness comes from the browser's crypto.getRandomValues / crypto.randomUUID API, a cryptographically secure source. No predictable generator such as Math.random is used, and no value is sent to a server.
What is the collision probability of two UUIDs?
A v4 has 122 bits of randomness. You would need to generate billions of UUIDs to see a collision — across 103 trillion UUIDs the collision chance is about one in a billion. In practical systems collisions are ignored.
How do I generate a UUID in .NET?
In .NET, Guid.NewGuid() produces a random v4-like GUID. With .NET 9+, Guid.CreateVersion7() produces a time-ordered v7 — preferred as a primary key for insert-heavy tables.