What makes a UUID valid?

32 hex digits in an 8-4-4-4-12 grouping (hyphens optional for many parsers), a variant in the top bits of the third group, and — for ids anyone will actually read — a version nibble the spec defines. Anything else is a random 128-bit string wearing a UUID's clothes.

Why does one of my ids report version 15?

That is MAX, defined in RFC 9562 as the all-ones upper bound for range queries. A version nibble of 9–14 on a random id usually means a hand-rolled generator got the bits wrong, not a real standard version.

Can it decode the time from any UUID?

Only from the versions that store time: v1 (100-nanosecond precision), v6 (v1 reordered) and v7 (milliseconds). v4 and v5 have no timestamp to recover — the date field stays empty for those.

Does checking a UUID prove the record exists?

No. Syntax and field decoding are entirely local checks. Whether that id resolves to a row is a question only the system that issued it can answer.

Generators & Utilities Ready to use

UUID Validator & Inspector

Check any UUID or ULID and read what it contains: syntax, version, variant, node, and the creation timestamp encoded in v1 and v7 ids.

Operation

Inspect reads the version, variant, node and (for v1/v7) the creation time baked into an id you paste.

ID format

v4 for opaque primary keys; v7 or ULID when rows should insert in creation order.

How many

Written as

Ignored for ULID, which never carries hyphens.

UPPERCASE

Seed (optional)

Set a seed to get the same batch again — useful for fixtures and tests.

ID to inspect

This tool runs entirely in your browser. Your input never leaves your device.

About UUID Validator & Inspector

Most validators only answer 'is this 8-4-4-4-12 hex'. That catches typos and nothing else. This tool parses the id and reports the fields RFC 9562 actually defines: the version nibble, the variant bits, time-low, time-mid, time-high, clock sequence and node — and, for the time-based versions, the moment the id was minted.

That decoding is genuinely useful in debugging. A row that should not exist has a v7 key, and the timestamp tells you which deploy created it. Someone has stored a UUID that is really a NIL placeholder (all zeros), and the inspector says so instead of your foreign key failing mysteriously later. A client sends a ULID into a UUID column and you find out before the database does.

Everything happens locally in your browser: paste ids, nothing is transmitted. Valid syntax is not proof of existence — no checker can tell you a UUID refers to a real record, only that it is well formed and what it says about itself.