KSUID Generator — K-Sortable Base62 Unique IDs
Generate KSUID strings online — 27-character Base62, 32-bit UTC timestamp + 128-bit randomness. Time-sortable, human-typeable, no delimiters. Designed by Segment for high-volume event streams. 100% local.
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Frequently Asked Questions
What is a KSUID?
KSUID (K-Sortable Unique IDentifier) was created by Segment for high-volume event ingestion. Each KSUID is 20 bytes: 4 bytes of Unix seconds since the KSUID epoch (2014-05-13) followed by 16 bytes of randomness, encoded as 27 Base62 characters. Sorting lexicographically also sorts by creation time.
How is KSUID different from ULID?
Both are time-sortable IDs. ULID has millisecond timestamp precision (48 bits) and 80 bits of randomness; KSUID has second precision (32 bits) but 128 bits of randomness. ULID uses Crockford Base32; KSUID uses Base62. For most workloads either is fine — pick based on which ecosystem your libraries already support.
When will KSUIDs run out?
The 32-bit second counter (from 2014-05-13) exhausts on 2150-06-19. Roughly 136 years is normally described as 'plenty of time', though rewriting your ID scheme in 2140 is still a task someone will inherit.
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