UUID v7 generator.

Worked example

The UUID already in the decoder, 01a16b35-0800-7a3f-9c2e-4d8b1f6a0e57, is a v7 we built by hand for 8:00 PM ET on Oct 23, 2026. Its first 12 hex digits, 01a16b350800, are the number 1,792,800,000,000: milliseconds since 1970, which is 2026-10-24 00:00:00.000 UTC. The 7 that starts the third group is the version. The 9 that starts the fourth group is binary 1001: its top two bits, 10, mark the RFC 9562 variant. Everything else is random.

How it works

• Layout of a v7. 48 bits of Unix time in milliseconds, 4 version bits (0111), 12 bits rand_a, 2 variant bits (10), 62 bits rand_b. Because the time comes first, v7 UUIDs sort by creation time as plain strings and as bytes, which keeps database B-tree inserts at the end of the index (RFC 9562, section 5.7).
• Monotonic mode. Several IDs made in the same millisecond would otherwise sort randomly among themselves. With Monotonic on, rand_a is used as a counter that starts at a random value each new millisecond and goes up by one for every ID inside it: method 1 of RFC 9562, section 6.2. If the counter runs out, the time field moves forward one millisecond.
• Decoding other versions. v1 and v6 carry a 60-bit count of 100-nanosecond steps since Oct 15, 1582 (v6 stores it high bits first so it sorts). v4 is 122 random bits with no time inside. v3 and v5 are hashes of a name. The variant tells you which spec the bits follow.
• Privacy. A v7 shows when it was made, to the millisecond. Don't use one as a public ID if the creation time is a secret.

Sources

• RFC 9562: Universally Unique IDentifiers (UUIDs), IETF, May 2024, read Oct 23, 2026

Related

• We tested the UUID v7 libraries: which ones really sort
• Unix timestamp converter
• Snowflake ID decoder

Who made this

Matt Busel, who tested UUID v7 libraries for this write-up. Generation and decoding happen on your device; nothing you paste leaves this page.