UUID Generator

UUID v4 (Universally Unique Identifier version 4) is a 128-bit number generated using random or pseudorandom numbers. It is formatted as 32 hexadecimal digits separated by hyphens in the pattern 8-4-4-4-12, for example: 550e8400-e29b-41d4-a716-446655440000. The 'v4' indicates the version, where version 4 is purely random unlike other versions that use timestamps or MAC addresses.

UUID v4 uses cryptographically random bytes, making it unpredictable and statistically unique. This tool specifically uses crypto.randomUUID(), which is backed by the browser's cryptographically secure pseudorandom number generator (CSPRNG) — the same source used for encryption keys. This makes the output suitable for security-sensitive use cases.

The probability of generating a duplicate UUID v4 is astronomically small. With 122 bits of randomness, you would need to generate approximately 2.71 quintillion UUIDs (2.71 × 10^18) to have a 50% chance of a single collision. In practice, UUID collisions are essentially impossible for any realistic workload.

Use UUIDs when you need to generate IDs across multiple systems without a central coordinator, when you don't want to expose the number of records in your database through sequential IDs, or when merging records from multiple sources. Use sequential integer IDs when you need guaranteed ordering, smaller storage size, or better database index performance on a single system.

No, UUIDs are case-insensitive. The hexadecimal letters a-f can be written in lowercase or uppercase and represent the same value. By convention, UUIDs are typically written in lowercase. When comparing or storing UUIDs, normalize them to a consistent case to avoid subtle bugs.