Create random unique IDs (UUID version 4, also called GUIDs) for your databases, files and code. Choose how many you need, generate them instantly, and copy with one click. They are made in your browser using secure randomness.
About this UUID generator
A UUID (universally unique identifier) — also known as a GUID on Microsoft systems — is a long ID like 550e8400-e29b-41d4-a716-446655440000. Developers use them to label database records, files, API requests and sessions with an identifier that is practically guaranteed to be unique, even across different machines and databases, without any central authority handing out numbers. This tool creates version 4 UUIDs, the most popular kind, built from random data so they reveal nothing about when or where they were made. You can generate up to 100 at once and copy them all in one tap. The randomness comes from your browser's built-in cryptographically secure generator, and nothing ever leaves your device.
Frequently asked questions
- What is a UUID?
- A 36-character ID (also called a GUID) used to label things uniquely — database rows, files, sessions.
- What is version 4?
- A UUID built from random numbers — the most common type, because it leaks no time or hardware info.
- Are they safe to use?
- Yes — generated in your browser with a cryptographically secure random source, never uploaded.
Understanding UUID v4 architecture
A version 4 UUID is a 128-bit value defined by the RFC 4122 standard. It consists of 32 hexadecimal digits displayed in five groups separated by hyphens. Within these 128 bits, 122 bits are generated using a cryptographically secure pseudorandom number generator, while the remaining 6 bits are reserved to indicate the version and the variant. This structure ensures that the identifier remains compatible with systems expecting a specific format while maintaining an extremely high level of entropy.
The generation process relies on filling the reserved bits with fixed values to satisfy the protocol requirements. Specifically, the bits representing the version are set to the value four, and the bits representing the variant are set to identify the UUID as a Leach-Salz variant. The rest of the bits are populated entirely by random data harvested from the system entropy pool. Because the probability of two independent processes generating the exact same 122-bit sequence is astronomically low, these identifiers are considered globally unique for all practical computing purposes.
The most common mistake when implementing these identifiers involves using a non-cryptographic random number generator to create the values. Standard library functions in many programming languages are designed for speed rather than security and may produce predictable sequences if seeded improperly. If the entropy source is weak or the seed is reused, the likelihood of a collision increases significantly, which can lead to data corruption or security vulnerabilities in distributed systems. Developers should always utilize established cryptographic libraries rather than basic math-based random functions to ensure the integrity of their unique identifiers.