ULID Generator

Generate sortable ULIDs online instantly, single or in bulk — free ULID generator.

Format

Each ULID starts with the current millisecond timestamp encoded in Crockford Base32, so ULIDs generated later always sort after earlier ones.

About

About the ULID Generator

Generates ULIDs — 26-character identifiers made of a timestamp and random bits that sort in order of creation.

Developers use it to generate sortable primary keys for databases where insertion order matters, while API designers use it for resource IDs that double as a rough creation timestamp. It's one of many free generators on Toolapt, and like every tool here, it's free to use with no sign-up and no limit on how many times you run it.

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Guide

Using the ULID Generator

  1. 1

    Step 1

    Enter how many ULIDs to generate.

  2. 2

    Step 2

    Optionally turn on lowercase formatting.

  3. 3

    Step 3

    Click "Generate" to create the batch.

  4. 4

    Step 4

    Click "Copy" to copy them all, or "Clear" to start over.

  • Encodes the current millisecond timestamp in Crockford Base32, so later ULIDs always sort after earlier ones
  • Fills the remaining bits using the browser's cryptographically secure random source (crypto.getRandomValues)
  • Generates up to 500 ULIDs at once, each a fixed 26 characters long
  • Optional lowercase formatting for the whole batch
  • Uses Crockford Base32 encoding, which avoids the visually ambiguous characters I, L, O and U
  • Works entirely in your browser — no installs and no sign-up
  • Free to use, with no limit on how many times you run it
  • Fully responsive, so it works just as well on a phone as on a desktop

Developers

Developers use the ULID Generator for sortable primary keys in databases where insertion order matters.

API designers

API designers use the ULID Generator for resource IDs that double as a rough creation timestamp.

Distributed systems engineers

Distributed systems engineers use the ULID Generator for identifiers that stay unique and roughly ordered across multiple services.

QA engineers

QA engineers use the ULID Generator for producing a batch of unique, sortable test identifiers at once.

Examples

ULID Generator examples

3 worked examples

01

A single ULID

Generating 1 ULID might produce 01ARZ3NDEKTSV4RRFFQ69G5FAV — the ULID spec's own canonical example; your generated value will differ.

02

Lowercase formatting

Turning on "Lowercase" re-cases the same value to 01arz3ndektsv4rrffq69g5fav, without changing what it represents.

03

The timestamp prefix

The first 10 characters of any ULID, such as 01ARZ3NDEK, encode the millisecond creation time in Crockford Base32.

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FAQ

Frequently asked questions

Quick answers to common questions about the ULID Generator.

What does the ULID Generator do?

It generates ULIDs — 26-character identifiers made of a timestamp and random bits, encoded in Crockford Base32.

Is the ULID Generator free to use?

Yes. It's free, with no sign-up, no watermark and no limit on how many times you use it.

Is my input safe when I use this tool?

Yes. Every ULID is generated entirely on your own device — nothing is sent to a server.

Are ULIDs cryptographically secure?

The random portion of each ULID is generated with your browser's crypto.getRandomValues API, not Math.random() or another predictable formula; the leading portion is always the current timestamp, which is by design not secret.

What's the difference between a ULID and a UUID?

Both are 128-bit unique identifiers, but a ULID encodes a millisecond timestamp first, so ULIDs sort chronologically as plain strings — a UUID (aside from version 7) generally doesn't.

Why does it use Crockford Base32 instead of hex?

Crockford Base32 is more compact than hex and deliberately excludes the letters I, L, O and U, which are easy to confuse with other characters or digits when read or typed.

Can I use the ULID Generator on my phone?

Yes. The page is fully responsive and works on mobile, tablet and desktop browsers alike.

Does the ULID Generator have any limitations?

It generates up to 500 ULIDs per batch, each with millisecond timestamp resolution.

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