UUID Generator
Random UUID v4 identifiers
Batch generation
How it works
UUIDs are generated using the browser's built-in
crypto.randomUUID() API, which uses a cryptographically secure random number generator. All UUIDs are generated locally and nothing is sent to the server.What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit identifier standardised by the Open Software Foundation in the 1990s and formalised in RFC 4122 (2005). It is displayed as 32 hexadecimal characters split into five groups by hyphens:
The core idea is that any system anywhere can generate an ID without coordinating with a central authority, and the probability of two independently generated UUIDs colliding is so astronomically small it can be treated as impossible in practice. Microsoft calls the same thing a GUID (Globally Unique Identifier), and it is the same format.
xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx (8-4-4-4-12).The core idea is that any system anywhere can generate an ID without coordinating with a central authority, and the probability of two independently generated UUIDs colliding is so astronomically small it can be treated as impossible in practice. Microsoft calls the same thing a GUID (Globally Unique Identifier), and it is the same format.
UUID versions
- v1: Generated from the current timestamp and the device's MAC address. Unique but reveals when and where it was created, which is a privacy concern.
- v3: Deterministic, generated by hashing a namespace and name with MD5. The same inputs always produce the same UUID.
- v4: Randomly generated (122 random bits). The most widely used version today, containing no timestamp nor MAC address. Just randomness. This is what this tool generates.
- v5: Like v3 but uses SHA-1 instead of MD5.
- v7: A newer standard (RFC 9562, 2024) combining a Unix timestamp prefix with random bits, making UUIDs sortable by creation time, which is useful for database primary keys.
How unique is "unique"?
A v4 UUID has 122 bits of randomness (6 bits are fixed for version/variant markers). The total number of possible v4 UUIDs is 2¹²², totally about 5.3 × 10³⁶. To have a 50% chance of a single collision you would need to generate approximately 2.7 × 10¹⁸ UUIDs. At a rate of one billion UUIDs per second that would take over 85 years. For any realistic application, collisions are not a concern.