Generate version 4 (random) UUIDs: 128-bit identifiers unique enough that two created independently, on different machines with no central coordination, will effectively never collide. They are produced in your browser with the Web Crypto API, with optional hyphens and uppercase, and nothing is sent to a server.
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit value used to uniquely identify information, generated in a way that makes collisions between two independently created UUIDs virtually impossible — even across different machines with no central coordination. This tool generates version 4 (random) UUIDs entirely inside your browser using the Web Crypto API; nothing is sent to or stored on a server.
How to Generate a UUID
- Choose a format — use the "Include Hyphens" and "Uppercase" checkboxes to pick the notation you want.
- Set the count — enter how many UUIDs to create at once (up to 50) in "Number to Generate".
- Generate — click the "Generate UUID" button and they are created instantly inside your browser.
- Copy — use each item's "Copy" button or the "Copy All" button to put them on your clipboard.
What is a v4 (random) UUID?
A version 4 UUID is built by filling most of the value (122 bits) with random data. It does not use information such as the time or a device's MAC address, so it is hard to predict, and this tool uses the cryptographically secure Web Crypto random source. Per the standard, the version digit is always 4 and the variant digit is always one of 8, 9, a, or b.
Where are UUIDs used?
UUIDs are commonly used as database primary keys, session and request-tracing IDs, filenames for uploaded files, and unique identifiers for records in distributed systems where multiple machines need to generate IDs independently without risk of collision.
Can two UUIDs collide?
In theory it is possible, but the probability is effectively zero. A v4 UUID has about 5.3×10³⁶ possible values, so even generating a billion per second you would wait decades before expecting a single collision. That is why they can be safely used as unique identifiers without any central coordination.
Are generated UUIDs stored?
No. Every UUID is generated only inside your browser and is never sent to or stored on a server. Refreshing the page clears the results, so copy any values you need beforehand.