UUID Inspector (Version, Variant, Time)
Developer
A UUID isn't just a random string — its 128 bits encode a version and variant, and the time-based versions carry a real timestamp. This inspector parses any UUID (canonical, braced, or urn:uuid: form) and tells you exactly what it is: the version number and name (v1 time+node, v2 DCE, v3 MD5 name-based, v4 random, v5 SHA-1 name-based, v6 reordered time, v7 Unix-epoch time, v8 custom), and the variant (RFC 4122, legacy NCS, or Microsoft). For v1 and v6 it decodes the 60-bit Gregorian timestamp to a real date, plus the clock sequence and the node — flagging whether the node is a real unicast MAC or a random multicast address. For v7 it reads the 48-bit Unix-millisecond timestamp. The nil and max UUIDs are recognised too. It's the fast way to answer "when was this created?" or "is this really a v4?" Everything runs locally; nothing is uploaded.
v1/v6 carry a Gregorian timestamp; v7 a Unix-ms timestamp; v4 is random. Variant is read from the bits, not guessed.
How to use
- Paste a UUID (with or without dashes, braces, or a urn:uuid: prefix).
- Read the version and variant; for v1/v6/v7 the creation timestamp is decoded automatically.
- Use the copy buttons for the canonical form or the timestamp.
Frequently asked questions
- Which versions carry a timestamp?
- v1 and v6 embed a 60-bit count of 100-nanosecond intervals since 1582-10-15 (the Gregorian reform), which this tool converts to a normal date. v7 embeds a 48-bit Unix millisecond timestamp in its first bits. v3, v4, v5, and v8 do not carry a decodable time — v4 is fully random, v3/v5 are hashes of a name, and v8 is implementation-defined.
- How is the version determined?
- The version is the high nibble of the 7th byte (the first hex digit of the third dash-group). The variant comes from the top bits of the 9th byte: 10x is RFC 4122, 0xx is the legacy NCS layout, and 110x is the Microsoft GUID layout. Both are read directly from the bits, so the answer is exact.
- What does the node / MAC tell me?
- In a v1 or v6 UUID the last 48 bits are the node. Classic v1 used the generating machine's MAC address (a privacy concern), but modern libraries use a random value with the multicast bit set. This tool shows the node and flags whether that multicast bit indicates a random node or a real unicast MAC.
- Is the decoded time trustworthy?
- It's exactly what's encoded in the UUID, so it's reliable as long as the generator's clock was correct and it really is the version it claims. A forged or hand-edited UUID can carry any timestamp, so treat the time as informative, not as proof.
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