Free Online UUID Generator
Generate cryptographically random UUID v4 identifiers instantly. Create single or bulk UUIDs with one click. Uses secure crypto.getRandomValues().
What Is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit identifier that is practically guaranteed to be unique across all space and time. UUIDs are formatted as 32 hexadecimal digits displayed in five groups separated by hyphens (e.g., 550e8400-e29b-41d4-a716-446655440000). They are used extensively in software development for database keys, session IDs, and distributed systems.
UUID v4 — Random Generation
UUID version 4 is generated using random or pseudo-random numbers. This tool uses the cryptographically secure crypto.getRandomValues() API to generate truly random UUIDs. The version number (4) is encoded in the UUID itself — the 13th hex digit is always 4, and the 17th digit is always 8, 9, a, or b, as specified by RFC 4122.
When to Use UUIDs
UUIDs are ideal when you need unique identifiers without a central authority. Common use cases include database primary keys (especially in distributed databases), API request tracking, file naming to avoid collisions, session tokens, and message queue identifiers. The probability of generating a duplicate UUID v4 is astronomically low — about 1 in 2^122.
Frequently Asked Questions
What is the chance of a UUID collision?
The probability of a UUID v4 collision is extremely low. You would need to generate about 2.71 quintillion UUIDs to have a 50% chance of a single collision. For practical purposes, UUID v4 values are unique.
What is the difference between UUID and GUID?
UUID and GUID (Globally Unique Identifier) are essentially the same thing. GUID is the term used primarily by Microsoft, while UUID is the standard term from RFC 4122. Both refer to 128-bit identifiers.
Why does the UUID have specific digits?
In UUID v4, the 13th hex digit is always 4 (indicating version 4) and the 17th digit is always 8, 9, a, or b (indicating the variant). This is defined by RFC 4122 and helps identify the UUID version.
Are these UUIDs cryptographically secure?
Yes. This tool uses crypto.getRandomValues() which provides cryptographically secure random numbers. The UUIDs are generated entirely in your browser with no server communication.
Can I use UUIDs as database primary keys?
Yes, UUIDs are commonly used as primary keys, especially in distributed databases. However, they are larger than auto-increment integers (16 bytes vs 4-8 bytes) and can impact index performance in some databases. Consider using ordered UUID variants for better B-tree performance.