UUID Decoder
Decode a UUID or ULID: version, variant and embedded timestamp.
About this tool
Paste a UUID or GUID in any format (hyphenated, braced, urn:uuid: or plain hex), or a ULID. The tool shows the version and what it means, the variant, any embedded timestamp in UTC and Unix milliseconds, the clock sequence and node for time-based versions, and the canonical, uppercase, braced, URN, hex and base64 forms.
What's inside a UUID
A UUID is 128 bits, normally written as 32 hex digits in five groups. The first digit of the third group is the version. v4 is random (122 random bits). v1 holds a 60-bit timestamp counting 100-nanosecond intervals since 15 October 1582, a clock sequence and a 48-bit node that is often the generating machine's MAC address. v6 is v1 reordered so it sorts by time. v7, standardised in RFC 9562 (2024), starts with a Unix millisecond timestamp, so new IDs sort in creation order, which is great for database indexes. v3 and v5 are MD5 and SHA-1 hashes of a name, and v8 is vendor-defined. The variant bits show whether a UUID follows the RFC layout or is a legacy Microsoft GUID. ULIDs are 26-character Crockford Base32 IDs whose first 10 characters are a millisecond timestamp. The decoder's v1 and v6 timestamps and clock sequences match Python's uuid module. Honest limits: timestamps only mean something in time-based versions, and anyone can create a UUID with arbitrary digits, so treat the time as a hint, not proof. v1's node can expose a MAC address, which is one reason v7 is now preferred. The UUID generator, the timestamp converter and the MAC address generator are related.
Frequently asked questions
How do I tell which version a UUID is?
Look at the first digit of the third group: in 018f3c6e-7b2a-7c4d-…, the 7 means version 7.
Can I get the creation time from a UUID?
Yes, for v1, v6 and v7 UUIDs (and ULIDs). v4 UUIDs are random and contain no time.
What is the difference between a UUID and a GUID?
Nothing in practice. GUID is Microsoft's name. Some legacy GUIDs use a different variant.
Is anything uploaded?
No. Everything runs in your browser and nothing is stored or sent.