Question 1

What's the difference between UUID v4 and UUID v7?

Accepted Answer

UUID v4 is fully random with no embedded information, which makes it unpredictable but causes poor index locality when used as a database primary key. UUID v7 embeds a 48-bit millisecond timestamp at the start, so IDs generated later always sort after earlier ones — much friendlier for database indexes while still being effectively unguessable.

Question 2

What is a ULID and how is it different from a UUID?

Accepted Answer

A ULID is a 26-character, Crockford Base32-encoded identifier that, like UUIDv7, starts with a sortable millisecond timestamp followed by random bits. It's case-insensitive, URL-safe without escaping, and slightly more compact and human-typeable than a UUID.

Question 3

Can this tool decode an existing UUID or ULID?

Accepted Answer

Yes — paste any UUID or ULID into the Inspect field and it reports the detected version, variant, and (for v1, v7, and ULID) the exact embedded creation timestamp.

UUID & ULID Generator

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