UUID & ULID generator

How to use this tool

1. Pick the type: v4, v7, ULID or v5, or Check an existing ID.
2. Set how many you need, up to 500, and any format options.
3. For v5, choose a namespace and type the name, one per line.
4. Copy one ID, copy them all, or download a text file.

How it works

A UUID is a 128-bit identifier written as 32 hexadecimal digits in five groups, such as 3f2b9c1e-8d4a-4b6f-9e21-7c5d0a1b2c3d. Version 4 is fully random, with 122 random bits, so two computers can create IDs without ever talking to each other. Version 7 puts the creation time in milliseconds at the front, so new IDs sort after old ones, which keeps database indexes compact. Version 5 is made from a namespace and a name with SHA-1, so the same input always gives the same UUID.

A ULID is also 128 bits but is written as 26 characters of Crockford Base32, with a 48-bit timestamp first. It sorts as text in creation order and avoids look-alike letters. Within one millisecond this generator counts upwards, so a batch stays in order.

Good to know

Which one should you use? For general unique IDs, v4 is the safe default. For primary keys in a database, v7 or ULID usually perform better because inserts land at the end of the index. Use v5 when you need a stable ID for the same thing every time, such as a URL. Avoid v1 for new work, because it can reveal the time and the network card of the machine that made it.

The Check option reads any UUID and tells you its version and variant. For v1, v6 and v7 UUIDs and for ULIDs it also shows the creation time stored inside. All IDs are generated on your device with the browser's cryptographic random source and are not stored or sent anywhere.