UUID Version Checker
Paste a UUID to see what it is made of. The checker reads the version and variant fields, explains how that kind of UUID is generated, and decodes the creation time from time-based UUIDs: the Gregorian timestamp, clock sequence and node of version 1 and 6, and the Unix millisecond timestamp of version 7.
- Runs in your browser
- No sign-up
- Free to use
How to use UUID Version Checker
- Paste a UUID or GUID.
- Read the version and what it means.
- For version 1, 6 or 7, read the timestamp.
- Check the variant to confirm it is a standard UUID.
UUID Version Checker features
All versions
Versions 1 to 8, plus the nil and max UUIDs.
Timestamps
Creation time of version 1, 6 and 7 UUIDs in ISO 8601.
Node analysis
Tells whether a version 1 node is a MAC address or random.
Variant
RFC 9562, NCS, Microsoft or reserved.
Field layout
Points to the version and variant digits.
Private
Runs in your browser.
When to use UUID Version Checker
- Finding when a record with a version 7 ID was created.
- Checking whether IDs leak machine addresses (version 1).
- Confirming a library generates the version you expect.
- Debugging sort order of UUID keys.
UUID Version Checker FAQ
How do I tell a UUID’s version?
Look at the 13th hexadecimal digit, the first digit of the third group: in 0192f1a8-3c4e-7a1b-… it is 7.
Can I get the creation date of any UUID?
Only from time-based versions: 1, 6 and 7. Version 4 is random, and versions 3 and 5 are hashes, so they contain no time.
Does a version 1 UUID reveal my computer?
It can: the last 12 digits may be the network card’s MAC address. Modern generators often use a random node instead, marked by the multicast bit, which the checker reports.
Why use version 7?
Version 7 UUIDs start with a millisecond timestamp, so they sort by creation time and keep database indexes efficient, while still containing 74 random bits.
What is the variant?
Bits in the 17th digit that say which specification the UUID follows. Standard UUIDs have 8, 9, a or b there.
Is the UUID sent anywhere?
No.
What is inside a UUID
A UUID looks like 32 random hex digits, but most versions have structure. Four bits record the version, two or three bits record the variant, and depending on the version the rest holds a timestamp, a counter, a machine identifier, a hash of a name or random bits.
Time-based UUIDs carry their creation time. Version 1 counts 100-nanosecond intervals since 15 October 1582, the start of the Gregorian calendar, split across the first three groups in an awkward order; version 6 stores the same timestamp in sortable order. Version 7, standardised in RFC 9562 in 2024, stores milliseconds since 1970 in the first 48 bits.
That information can be useful, for example to see when a record was created, and it can be a privacy issue. Version 1 UUIDs made with a real MAC address identify the machine that generated them, which is one reason random version 4 and sortable version 7 UUIDs are now preferred.
Name-based UUIDs, versions 3 and 5, are hashes of a namespace and a name: the same input always produces the same UUID. They are handy for deterministic identifiers, such as an ID for a URL, but reveal nothing about time and should not be treated as secret.