UUID & ULID Inspector

How to use it

Paste a UUID or a ULID into the box. The inspector checks the format, tells you whether it is valid, and breaks the identifier down into its parts in real time — there is nothing to submit and no button to press. A UUID is 36 characters written as five hexadecimal groups in an 8-4-4-4-12 pattern, separated by hyphens. Two positions carry meaning: the version digit, which says how the UUID was generated, and the variant bits, which mark it as a standard RFC identifier. The inspector reads both for you — so it can tell a random version 4 from a time-ordered version 7 at a glance. A ULID is 26 characters in Crockford base32, and it is built to sort. Its first 10 characters encode a millisecond timestamp and the remaining 16 are random, which means ULIDs line up in creation order when sorted as plain text. When you paste one, the inspector decodes that leading timestamp back into a readable date and time. For any identifier that carries a time component — a version 1, 6, or 7 UUID, or a ULID — the tool surfaces the embedded timestamp so you can see exactly when it was minted. It also recognizes the two special UUIDs: the all-zero nil value and the all-ones max value. Everything is computed locally in your browser, so the identifier you paste is never uploaded. That makes the inspector a quick, safe way to debug a database row, confirm a value is a well-formed UUID before you store it, or check whether an ID sorts by creation time.

Frequently asked questions

Which UUID versions are recognized?

Versions 1 through 8, plus the special nil and max UUIDs. Timestamps are decoded for v1 (Gregorian time) and v7 (Unix time); v4 is random and has no timestamp.

What is a ULID?

A ULID is a 26-character, sortable identifier. Its first 10 characters encode a 48-bit millisecond timestamp, which this tool decodes to a UTC date.

Does it generate new IDs?

No — this tool inspects existing identifiers. To generate a random UUID, use the random generator. Nothing you paste is uploaded.

What is the difference between a UUID and a ULID?

Both are 128-bit unique identifiers, but they differ in format and sortability. A UUID is 36 hexadecimal characters in an 8-4-4-4-12 pattern, and most versions are unordered; a ULID is 26 Crockford base32 characters whose leading bits encode a timestamp, so ULIDs sort chronologically as plain text. If you want database keys that naturally order by creation time, a ULID — or a time-ordered version 7 UUID — is usually the better choice.