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ULID Generator

Generate ULIDs one at a time or in bulk: sortable, timestamp-prefixed identifiers in Crockford base32. Use monotonic mode for strictly ordered ids, decode any ULID back to its timestamp, and copy the results as a plain list.

Everything runs locally in your browser. Your data never leaves your device.

Ids created within the same millisecond increment the previous randomness by one, so the whole batch sorts strictly in creation order.

Result

Generating…

TimestampRandomness

Decode a ULID

Lowercase works too, and the look-alikes I, L and O read as 1, 1 and 0.

Next steps

Send this tool's output straight into another tool.

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About the ULID Generator

This tool generates ULIDs, sortable unique identifiers made of a 48-bit millisecond timestamp and 80 bits of randomness, written as 26 Crockford base32 characters. Make one or up to 1,000 at a time, with the timestamp and randomness characters color-coded so you can see the two parts.

It also works in reverse: paste any ULID into the decode panel to see when it was created, as a readable date, along with its random bits as hex.

What you can do

  • Generate a single ULID or a bulk list of up to 1,000.
  • Generate strictly ordered ids with monotonic mode.
  • Decode a ULID back to its creation timestamp.
  • Extract the date and time embedded in any ULID.
  • Copy the whole list or download it as a text file.
  • Switch the output to lowercase.

How to use the ULID Generator

  1. 1Set how many ULIDs you need and click Regenerate for a fresh batch.
  2. 2Turn on monotonic mode if ids created within the same millisecond must keep their creation order.
  3. 3Copy the result, or download the list as a text file.
  4. 4To inspect an id, paste it into the decode panel and read its timestamp and randomness.

How a ULID is put together

The first 10 characters encode the creation time in milliseconds since the Unix epoch, and the remaining 16 encode 80 bits of randomness. Because the timestamp comes first, sorting ULIDs alphabetically sorts them by creation time, so newer ids always land at the end of an index. The Crockford base32 alphabet leaves out I, L, O and U, so ids are hard to misread, and the decoder here is equally forgiving: lowercase input works, and a pasted I, L or O is read as 1, 1 or 0.

A ULID holds 128 bits, the same as a UUID, in 26 characters instead of 36. If you need standard UUIDs instead, the UUID Generator makes them, and its version 7 solves the same sortability problem in UUID form. For shorter ids with a configurable alphabet, use the Nano ID Generator.

What monotonic mode does

Two ULIDs created in the same millisecond share a timestamp, so their order comes down to their random parts. In monotonic mode the generator follows the spec: within one millisecond each new id reuses the previous randomness incremented by one, so the whole batch sorts strictly in creation order. The guarantee covers ids from one generator run, not ids created on different machines.

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