UUID Generator
Generate random v4 UUIDs instantly.
What is a UUID and what is it used for?
UUID (Universally Unique Identifier) is a standard 128-bit identifier defined in RFC 4122. Several versions exist: UUID v1 uses the timestamp and MAC address; UUID v3 and v5 generate identifiers based on a namespace and name; and UUID v4, the most widely used, generates completely random identifiers. The probability of collision in UUID v4 is astronomically low.
UUIDs are fundamental in modern software development. They are used as primary keys in distributed databases (like DynamoDB or Cassandra), as resource identifiers in REST APIs, for user session tracking, file systems, and as transaction identifiers in microservicios. Their main advantage over sequential IDs is that they can be generated independently on any node without central coordination.
Frequently asked questions
Can UUIDs repeat?
Technically yes, but the probability is so low that it is considered practically impossible. A UUID v4 has 2^122 possible combinations (approximately 5.3 x 10^36). To have a 50% probability of collision, you would need to generate about 2.7 quintillion UUIDs.
What is the difference between UUID v1 and v4?
UUID v1 includes the timestamp and MAC address of the machine, which allows chronological ordering but exposes hardware information. UUID v4 is completely random, offers greater privacy, and is the most recommended for general use.
What are UUIDs used for?
They are used as unique identifiers in databases, APIs, distributed systems, session tracking, device identification, and any scenario where a unique ID is needed without relying on a central server to generate it.
Want to learn more? Read our complete guide →