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ULID Generator

Generate ULIDs — time-sortable unique IDs — in bulk, with monotonic mode and a timestamp decoder. A modern, sortable alternative to UUIDs. Free.

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Enter a valid 26-character ULID to see when it was created.

💡 About ULIDs

  • A ULID is a 26-character identifier: a 48-bit timestamp followed by 80 bits of randomness.
  • Because the timestamp comes first, ULIDs sort in creation order — great for database keys.
  • They use Crockford's Base32 (no I, L, O, or U), so they are URL-safe and easy to read.

Free ULID Generator

Generate ULIDs — universally unique, lexicographically sortable identifiers — in bulk, right in your browser. Create up to 1,000 at once, use monotonic mode for guaranteed ordering, and even decode a ULID's creation time. A modern, sortable alternative to UUIDs. Free, no sign-up.

What is a ULID?

A ULID (Universally Unique Lexicographically Sortable Identifier) is a 128-bit identifier written as 26 characters. Unlike a random UUID, a ULID starts with a 48-bit timestamp, so identifiers created later always sort after earlier ones. The remaining 80 bits are random, giving the same practical uniqueness as a UUID. The result is an ID that is both globally unique and naturally ordered by creation time.

ULID vs UUID

Both are 128-bit unique identifiers, but they solve different problems:

  • Sortability — ULIDs sort by creation time; random UUIDs (v4) do not.
  • Encoding — ULIDs use 26 Crockford Base32 characters; UUIDs use 36 characters with hyphens.
  • Readability — ULIDs omit ambiguous letters (I, L, O, U) and are URL-safe with no special characters.
  • Database performance — time-ordered keys reduce index fragmentation compared with random UUIDs.

How to use the ULID generator

It is instant:

  • Choose how many ULIDs to generate (up to 1,000).
  • Enable monotonic mode if you need strict ordering within the same millisecond.
  • Toggle lowercase if your system prefers it.
  • Copy the list or download it as a text file.

How ULIDs stay sortable

The first 10 characters of a ULID encode the number of milliseconds since the Unix epoch. Because that timestamp leads the string, sorting ULIDs alphabetically is the same as sorting them by time. When many IDs are created in the same millisecond, monotonic mode increments the random part instead of regenerating it, so even those keep a stable, increasing order — useful for high-throughput inserts.

Why developers choose ULIDs

ULIDs are popular for database primary keys and distributed systems. Their time-ordered nature keeps B-tree indexes compact and inserts fast, avoiding the write amplification that random UUIDs can cause. They can be generated anywhere without coordinating with a central server, they are safe to expose in URLs, and they carry a rough creation timestamp you can decode later — which this tool lets you do.

Pro tip

Use monotonic mode when you generate many IDs in a tight loop and need guaranteed ordering. If you specifically need the classic UUID format instead — for example to match an existing schema — use our UUID Generator, which also offers the time-ordered UUID v7.

FAQ

Is this ULID generator free?
Yes. It is completely free, runs in your browser, and requires no account or sign-up.
What is the difference between a ULID and a UUID?
Both are 128-bit unique identifiers, but a ULID is time-sortable and uses 26 Base32 characters, while a random UUID is not sortable and uses 36 hyphenated hex characters. ULIDs are often preferred for database keys because they sort by creation time.
Are ULIDs sortable by time?
Yes. The first part of a ULID is a millisecond timestamp, so sorting ULIDs alphabetically sorts them by when they were created.
What is monotonic mode?
When several ULIDs are generated in the same millisecond, monotonic mode increments the random component instead of regenerating it, guaranteeing they remain in strict increasing order.
Can I get the creation time from a ULID?
Yes. The timestamp is embedded in the first 10 characters. Paste a ULID into the decoder in this tool to see exactly when it was created.
Are ULIDs safe to use in URLs?
Yes. ULIDs use Crockford Base32, which contains only letters and digits with no special characters, so they are URL-safe and avoid ambiguous characters like I, L, O, and U.
Are ULIDs as unique as UUIDs?
In practice, yes. Each ULID includes 80 bits of randomness per millisecond, making collisions vanishingly unlikely for normal use.

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Pro tip: pair this tool with Upside Down Text Generator and Text Similarity Checker for a faster SEO workflow.