Generate reproducible UUID v4 and v7 values from a seed, or validate any UUID or GUID and decode its version, variant and embedded timestamp.
017f22e2-79b0-7cc3-98c4-dc0c0c07398f is a version 7 (Unix Epoch time-based) UUID with the RFC 9562 variant; it was stamped at 2022-02-22 19:22:22.000 UTC.
Lower-case hex in 8-4-4-4-12 groups: 017f22e2-79b0-7cc3-98c4-dc0c0c07398f.
Leading bits 10 mean the RFC 9562 layout; 0, 110 and 111 are reserved for older or future schemes.
This layout leaves 74 bits for random data.
A UUID is a 128-bit identifier written as 32 hex digits in 8-4-4-4-12 groups. RFC 9562 fixes two fields in every standard UUID: the variant bits 10 at the start of the 17th hex digit, and a 4-bit version number in the 13th. The decoder reads both, then unpacks what that version carries: a 48-bit Unix millisecond timestamp for version 7, a 60-bit count of 100-nanosecond intervals since 15 October 1582 for versions 1 and 6, or 122 random bits for version 4.
The default is the RFC 9562 version 7 example, 017f22e2-79b0-7cc3-98c4-dc0c0c07398f, whose first 48 bits count 1,645,557,742,000 ms, which is 22 February 2022 at 19:22:22 UTC. Developers pick v7 for database keys because the values sort by creation time.
Generated UUIDs come from a seeded xoshiro256** generator, so the same seed always gives the same list. For identifiers that must be unguessable, use a cryptographic source such as crypto.randomUUID().
Checked against: RFC 9562 Appendix A.6 (Tuesday, February 22, 2022 2:22:22.00 PM GMT-05:00); Python 3.8: int('017F22E279B0', 16) = 1645557742000
Checked against: RFC 9562 Appendix A.3; Python 3.8 uuid.UUID(...).version = 4, .variant = 'specified in RFC 4122'
Checked against: RFC 9562 Appendix A.1; Python 3.8 uuid.UUID(...).time = 138648505420000000, (time − 122192928000000000) / 10^7 = 1645557742 s; .clock_seq = 13256; .node = 0x9f6bdeced846
Checked against: RFC 9562 Appendix A.5 (same instant as the v1 example)
Version 4 fills 122 of the 128 bits with random data, so values are spread evenly and reveal nothing. Version 7, defined in RFC 9562 (May 2024), puts a 48-bit Unix millisecond timestamp first and 74 random bits after it, so new IDs sort in creation order. RFC 9562 notes that v4 has poor database-index locality, which is why v7 suits primary keys, at the cost of revealing when each ID was made.
In practice, no. A v4 UUID has 122 random bits, so by the birthday bound you would need about 2.7 × 10^18 of them for a 50% chance of a single duplicate, or about 103 trillion for a one-in-a-billion chance. Real collisions come from faulty random number generators or reused seeds, which is why the seeded UUIDs here shouldn't be used where uniqueness across systems matters.
They are the same 128-bit format; GUID is Microsoft's name for it. Microsoft tools often print GUIDs in upper case inside braces, such as {017F22E2-79B0-7CC3-98C4-DC0C0C07398F}, and RFC 9562 allows upper, lower or mixed case, so parsers should accept both. The one real difference is binary byte order: Windows stores the first three groups little-endian, which matters only when reading raw bytes.
Take the first 12 hex digits, which hold a 48-bit count of milliseconds since 1970-01-01 00:00 UTC, and convert them to decimal. For 017f22e2-79b0-7cc3-98c4-dc0c0c07398f, 017f22e279b0 is 1,645,557,742,000 ms, which is 2022-02-22 19:22:22.000 UTC. The 48-bit field runs out in the year 10889, so it will not wrap in practice.
It can be. Version 1 stores a 60-bit timestamp and a 48-bit node field that is traditionally the machine's MAC address, so the ID reveals when and on which network card it was made; the RFC 9562 v1 example decodes to 2022-02-22 19:22:22 UTC with node 9f:6b:de:ce:d8:46. RFC 9562 allows a random node value instead, and says to use version 7 instead of 1 or 6 where possible.
Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 8 worked examples whose answers come from independent sources; for example, “RFC 9562 version 7 example” is checked against RFC 9562 Appendix A.6 (Tuesday, February 22, 2022 2:22:22.00 PM GMT-05:00); Python 3.8: int('017F22E279B0', 16) = 1645557742000.
RFC 9562 — Universally Unique IDentifiers (UUIDs), §4–5 and Appendix A test vectors; Blackman & Vigna — xoshiro256** and SplitMix64 reference code.
8 worked examples with independently sourced answers ship with this calculator. They run in the test suite; you can run them here too.
Check a password's entropy in bits and its average brute-force crack time at a chosen guess rate, or generate a password from a reproducible seed.
Generate MD5, SHA-1, SHA-256, SHA-512 and CRC-32 hashes of any text, check them against a published checksum, and see the avalanche effect.
Convert numbers between binary, decimal, hex, octal and any base 2–36, including fractions, repeating digits and two's-complement bits for negatives.
Encode or decode Base64, URL-safe Base64, URL percent-encoding, HTML entities, hex bytes and Unicode code points, with UTF-8 and UTF-16 byte counts.
Format (pretty-print) or minify JSON and validate it against RFC 8259, with the line and column of any syntax error explained in plain words.
Allow optional Google Analytics to measure page visits? Calculators work either way. Privacy and choices
Optional analytics: off.