Is my UUID sent to a server?

No. Decoding happens entirely in your browser — the value you paste never leaves your device or gets logged anywhere.

What's the difference between version and variant?

The variant (the first bits of the 17th hex digit) says which layout rulebook the UUID follows — almost every UUID you'll ever see is the RFC 9562/4122 variant. The version (the first digit of the 13th hex digit) only means something once you know the variant is RFC 9562, and it says which of the eight generation schemes (v1-v8) produced it.

Why does my UUID v1 leak my MAC address?

RFC 9562 defines v1's last 48 bits as a "node id", and the traditional implementation fills it with the generating machine's real network MAC address. Every v1 UUID from that machine then shares that same value forever — a stable, extractable identifier, plus the precise creation timestamp this page decodes. If the node id below doesn't have its lowest bit set, that's the shape of a real MAC rather than a randomly generated one.

Can a UUID v5 be reversed back to its namespace and name?

No — v5 (and v3) are one-way hashes of a namespace UUID plus a name string. You cannot recover the original inputs from the UUID alone. If you have a guess at what they were, use the UUID generator's v5 mode to check it: generate that namespace+name combination and compare the result to what you pasted here.

What's the difference between UUID and GUID?

Nothing structurally — GUID is Microsoft's name for the same 128-bit layout this page decodes.

This tool runs entirely in your browser. Nothing you paste is uploaded.

How you can check →

UUID Decoder

Encoding & Decoding

Paste a UUID to see its version, variant, and — for v1, v6 and v7 — the real timestamp encoded inside it. Runs entirely in your browser.

Need to generate a UUID instead of decode one? The UUID generator makes every version — v1 through v8, plus Nil and Max.

UUID

Version and variant, decoded from the bits

This tool never guesses from a UUID's shape — it reads the version nibble and variant bits exactly as RFC 9562 (the current spec, which obsoletes the older RFC 4122) defines them, and says plainly when those bits don't resolve to a known version (an NCS, Microsoft, or future-reserved variant UUID has no "version" in the v1-v8 sense).

What the timestamp tells you

v1, v6 and v7 UUIDs each embed a real creation timestamp — v1/v6 as 100-nanosecond ticks since 1582-10-15, v7 as milliseconds since 1970-01-01. This page extracts it and shows both the UTC instant and your browser's local time, with a direct link to the epoch converter for further conversion. v3, v4, v5 and v8 UUIDs carry no timestamp at all — there's nothing to extract.

Common use cases

Checking whether a UUID a system gave you is actually the version you expect
Finding out exactly when a v1/v6/v7-keyed record was created, from the ID alone
Auditing whether a legacy v1 UUID is leaking a real MAC address
Verifying a v5 UUID against a namespace+name guess, via the generator

Frequently asked questions

Is my UUID sent to a server?: No. Decoding happens entirely in your browser — the value you paste never leaves your device or gets logged anywhere.
What's the difference between version and variant?: The variant (the first bits of the 17th hex digit) says which layout rulebook the UUID follows — almost every UUID you'll ever see is the RFC 9562/4122 variant. The version (the first digit of the 13th hex digit) only means something once you know the variant is RFC 9562, and it says which of the eight generation schemes (v1-v8) produced it.
Why does my UUID v1 leak my MAC address?: RFC 9562 defines v1's last 48 bits as a "node id", and the traditional implementation fills it with the generating machine's real network MAC address. Every v1 UUID from that machine then shares that same value forever — a stable, extractable identifier, plus the precise creation timestamp this page decodes. If the node id below doesn't have its lowest bit set, that's the shape of a real MAC rather than a randomly generated one.
Can a UUID v5 be reversed back to its namespace and name?: No — v5 (and v3) are one-way hashes of a namespace UUID plus a name string. You cannot recover the original inputs from the UUID alone. If you have a guess at what they were, use the UUID generator's v5 mode to check it: generate that namespace+name combination and compare the result to what you pasted here.
What's the difference between UUID and GUID?: Nothing structurally — GUID is Microsoft's name for the same 128-bit layout this page decodes.

UUID Generator

Generate every UUID version RFC 9562 defines — v1 to v8, one at a time or in bulk.

Epoch Converter

Paste any timestamp — seconds, ms, µs, ns, ISO, or SQL — and see what it is.

JWT Decoder

Decode a JSON Web Token's header and payload instantly.