UUID Generator
Generate random UUIDs (v4) instantly. Cryptographically secure, single or bulk — click to copy.
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. The standard text format uses 32 hexadecimal digits separated by four hyphens, creating a string like 550e8400-e29b-41d4-a716-446655440000. UUIDs are designed to be unique without a central registration authority.
UUID v4 (Random)
Version 4 UUIDs are generated using random or pseudo-random numbers. Of the 128 bits, 122 are randomly generated, while 6 bits identify the version (4) and variant. This generator uses the Web Crypto API for cryptographic-quality randomness.
x = random hex digit, 4 = version, y = 8/9/a/b (variant)
f47ac10b-58cc-4372-a567-0e02b2c3d479
6ba7b810-9dad-41d8-80b4-00c04fd430c8
550e8400-e29b-41d4-a716-446655440000
Collision Probability
With 122 random bits, there are approximately 5.3 × 10³⁶ possible v4 UUIDs. You would need to generate about 2.71 × 10¹⁸ UUIDs to have a 50% probability of one collision (the birthday paradox). Generating 1 billion UUIDs per second, it would take about 85 years to reach that threshold. For all practical purposes, v4 UUIDs are unique.
Common Use Cases
UUIDs are used as database primary keys (especially in distributed systems), API identifiers, session tokens, correlation IDs in microservices, file names for uploaded content, and transaction IDs. They're preferred over sequential IDs when you need uniqueness without coordination between systems.
Frequently Asked Questions
A 128-bit identifier formatted as 32 hex digits with hyphens. Designed to be unique without central coordination. Used as database keys, API IDs, and more.
Version 4 uses 122 random bits for generation. The 4 in the third group identifies it as v4. This generator uses the crypto-secure Web Crypto API.
Practically yes. With 5.3×10³⁶ possibilities, you'd need to generate 1 billion per second for 85 years to have a 50% collision chance.
Same thing. UUID is the standard term; GUID is Microsoft's name. Format and generation are identical.
Yes. It uses crypto.getRandomValues(), providing the same quality randomness used for encryption keys and security tokens.