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About

UUID Generator

A random version 4 UUID is ready as the window opens; ask for five or a thousand, and copy them as lines, a JSON array or an SQL list. Version 7 puts the time first so the IDs sort in the order they were made, versions 5 and 3 turn a name into the same UUID every time, and beside them are ULIDs and Nano IDs.

What it does

  • Version 4 at random; version 7 time-ordered, in order even when a thousand are made in one millisecond; version 1 with a random node.
  • Versions 5 and 3 from a name in the DNS, URL, OID or X.500 namespace, or your own; the Nil and Max UUIDs.
  • One to a thousand at a time, copied one by one or all at once, downloaded, or written as JSON or SQL.
  • Lower or upper case, without hyphens, in braces as .NET writes them, as a URN, or as 22 characters of URL-safe Base64.
  • ULIDs, which sort by time as plain text, and Nano IDs of any length and alphabet, with how long until a repeat is likely.
  • Inspect: paste a UUID or a ULID for its version, its variant and, where it carries one, the time it was made.

How to use it

  1. Pick the version, or ULID or Nano ID.
  2. Set how many and how they are written.
  3. Copy or download them.
  4. Paste any UUID into the inspector to read it.

What it does not do

  • Making versions 2, 6 and 8: they are read in the inspector, not made, since nobody asks for them.
  • A version 1 with your network card’s address: a web page cannot read it, and it has no place in an ID anyway.
  • KSUID, Snowflake and CUID2: each comes with its own library, and a system that needs one already has it.
  • An API: the IDs are made in your browser, and there is no server to ask.

Questions

Version 4 or version 7?

Version 4 when the order does not matter. Version 7 for database keys: ordered keys keep an index tidy, and the time the ID was made can be read back from it.

Are these really unique?

A version 4 UUID has 122 random bits. You would have to make about 2.7 quintillion of them before a duplicate became as likely as not.

Why does version 5 give the same UUID every time?

By design: it is built from the SHA-1 of the namespace and the name, so the same name maps to the same ID on every machine. Use it where two systems must agree on an ID without talking.

What is a ULID?

Twenty-six characters of Crockford’s base32 with the time first, so it sorts by creation time as plain text and has no hyphens. Underneath it is 128 bits, like a UUID.

Everything here runs in your browser. Nothing you type, paste or open is uploaded, and there is no account and no queue. How that works.

For one job

  • UUID v7 Generator: Version 7 UUIDs, which sort by the time they were made.
  • ULID Generator: ULIDs that sort by creation time, and the time read back from any ULID.
  • Nano ID Generator: Short random IDs of any length and alphabet, with the odds of a repeat.

Often used with

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