UUID Generator online

A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify objects in software systems. UUID v4 is randomly generated using a cryptographic random number generator, making collisions virtually impossible — the probability is astronomically small.

What is a UUID and How Does This Generator Work Online?

A UUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier), is a 128-bit value formatted as 32 hexadecimal digits split into five groups: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. This generator creates version 4 UUIDs using your browser's crypto.getRandomValues() API — the same cryptographically secure random number source used by password managers and security libraries. Nothing is sent to a server; every UUID is generated locally in your tab.

UUID Versions Explained

• v1 (time-based) — derived from the current timestamp and the MAC address of the machine. Reveals when it was created.
• v3 (MD5 namespace) — deterministic UUID generated by hashing a namespace and a name using MD5.
• v4 (random) — 122 bits of cryptographic randomness. The most widely used version. This is what this tool generates.
• v5 (SHA-1 namespace) — like v3 but uses SHA-1. Preferred over v3 for new applications.
• v7 (Unix timestamp) — sortable UUID using millisecond precision Unix timestamps. Increasingly popular for database primary keys.

Common Use Cases for UUIDs

UUIDs solve the problem of generating unique identifiers without a central coordinator. Unlike auto-incrementing integers, UUIDs can be created by any client or microservice without risk of collision.

• Primary keys in relational databases (PostgreSQL, MySQL, SQLite)
• Unique identifiers in NoSQL databases (MongoDB, DynamoDB, Firestore)
• Request correlation IDs for distributed system tracing and logging
• Session tokens and temporary link IDs (always combine with expiry)
• File and asset naming to avoid conflicts when uploading to object storage
• Idempotency keys in payment and API systems

Can Two Generated UUIDs Ever Be the Same?

In theory, yes. In practice, no. A version 4 UUID has 2^122 possible values — that's roughly 5.3 × 10^36 unique identifiers. To have a 50% chance of generating just one duplicate, you would need to generate approximately 2.7 × 10^18 UUIDs. At a billion UUIDs per second, that would take over 85 years. For any real-world application, UUID v4 collisions can be treated as impossible.