UUID generator. Random IDs, made on your device.

How to use the UUID Generator

This generator makes unique IDs in bulk: random UUID v4 values, the all zero NIL UUID, and ULIDs that sort by creation time. Random values come from your browser's Web Crypto API rather than Math.random. It is for developers who need IDs for database rows, test fixtures, config files or API keys in a hurry.

Step by step

1. 1
   Pick an ID type

   Under ID type, choose UUID v4 for random IDs, NIL UUID for the all zero placeholder, or ULID for time sortable IDs. Picking a type makes a new batch straight away. The page opens with 5 UUID v4 values already made.

2. 2
   Set how many you need

   Type a number in How many, from 1 to 100. The default is 5. A number above 100 is cut to 100, and anything below 1 becomes 1.

3. 3
   Choose the format

   Under Format, tick Uppercase for capital letters, untick Hyphens to get one unbroken 32 character string, or tick Wrap in braces to add curly brackets around each value. Hyphens is on by default. These options are grayed out for ULID, which is always uppercase with no hyphens.

4. 4
   Generate

   Press Generate to make a fresh batch. Every press, and every change to a format option, replaces the whole list with new values.

5. 5
   Copy or download

   Press Copy beside one ID to copy just that one, Copy all to copy the whole list with one ID per line, or Download .txt to save it as uuids.txt or ulids.txt.

Reading the result

• The line above the list shows the count and type, for example 5 items and UUID v4. Each row is numbered so you can refer to it.
• A UUID v4 has 36 characters in groups of 8, 4, 4, 4 and 12. The first digit of the third group is always 4, which marks the version, and the first digit of the fourth group is always 8, 9, a or b.
• The NIL UUID is 00000000-0000-0000-0000-000000000000 every time. Asking for several just repeats it.
• A ULID has 26 characters. The first 10 encode the time it was made, down to the millisecond, and the last 16 are random, so ULIDs made later sort after earlier ones.

Tips and common mistakes

• Changing Uppercase, Hyphens or Wrap in braces makes a brand new batch rather than reformatting the old one. Copy anything you need before you change an option.
• ULIDs from the same batch are usually made in the same millisecond and share their first 10 characters, so their order inside one batch is random.
• Use Wrap in braces for tools that expect GUIDs written as {value}, such as some .NET and Windows registry settings.
• Use the NIL UUID only as a placeholder or default value, never as a real ID, since it is the same everywhere.

Privacy and limits

Every ID is made in your browser with crypto.getRandomValues or crypto.randomUUID, and nothing is sent to a server. Nothing is saved either, so the list is gone when you reload. The tool would fall back to Math.random only in a very old browser with no Web Crypto support.

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