ULID Generator

What is a ULID?

A ULID is a 128-bit ID that starts with the time it was made, so ULIDs sort in creation order. It is written as 26 characters.

ULID stands for Universally Unique Lexicographically Sortable Identifier. The first 48 bits are the time in milliseconds and the last 80 bits are random. Sort ULIDs as plain text and they come out oldest first.

ULIDs use Crockford Base32: the digits 0 to 9 and the letters A to Z without I, L, O and U, which are easy to misread. The usual form is uppercase, but readers should accept either case. It is the same size as a UUID, so it fits a 16-byte UUID column too.

What a ULID looks like

Here is the ULID you just made, split into its parts. ClickTap Generate above and watch the end change.

• The first 10 characters are the time it was made: 48 bits, in milliseconds since 1970.
• The last 16 characters are random: 80 bits in total.

Its time part says it was made at the moment you opened this page.

When to use a ULID

Make a ULID in code

import { ulid, monotonicFactory } from 'ulid';

console.log(ulid());

// Strictly increasing, even within the same millisecond:
const next = monotonicFactory();
console.log(next(), next());

from ulid import ULID

id = ULID()
print(str(id))
print(id.datetime)  # when it was made

import com.github.f4b6a3.ulid.Ulid;
import com.github.f4b6a3.ulid.UlidCreator;

Ulid id = UlidCreator.getMonotonicUlid();
System.out.println(id.toString());

var id = Ulid.NewUlid();
Console.WriteLine(id.ToString());

import "github.com/oklog/ulid/v2"

id := ulid.Make()
fmt.Println(id)

use ulid::Ulid;

let id = Ulid::new();
println!("{id}");

ULID vs UUID v7, UUID v4 and Nano ID

Questions people ask