KSUID Generator

How to use

1. 1Pick how many KSUIDs to generate (1 to 500) and choose Current time to stamp each ID with the wall-clock second, or Custom date and time to key the batch to a specific moment.
2. 2Click Generate KSUIDs. Each row shows the 27-character base62 string and the ISO timestamp it carries; use the per-row Copy button or Copy all to take the whole list.
3. 3To inspect an existing KSUID, paste it into the Decode a KSUID box. The decoder shows the embedded timestamp, ISO date, the 16-byte random payload as hex, and the full 20-byte binary.
4. 4Use the Segment example, Nil KSUID, and Max KSUID sample buttons to see what valid edge values look like before pasting your own.
5. 5Click Restore defaults to return the batch size and timestamp source to their starting values.

About this tool

KSUID Generator and Decoder produces and parses K-Sortable Unique Identifiers in your browser, following the public Segment KSUID specification. A KSUID is a 160-bit value laid out as a 4-byte big-endian uint32 timestamp followed by a 16-byte random payload from crypto.getRandomValues, the same CSPRNG that backs crypto.randomUUID and SubtleCrypto in modern browsers. The timestamp is the number of seconds since the KSUID epoch, Unix-second 1400000000 (Tue May 13 2014 16:53:20 UTC), so the 4-byte field remains useful until the year 2150. Serialized form is exactly 27 characters of base62, drawn from the alphabet 0-9, A-Z, a-z, left-padded with the base62 zero character so every encoded value is the same length. Because the timestamp sits in the high-order bytes and base62 preserves order on equal-length strings, plain string comparison sorts KSUIDs by creation time, which makes them excellent database primary keys, event identifiers, idempotency tokens, log correlation IDs, and S3 object keys. Generate a single KSUID, a batch of up to 500, or a batch keyed to a custom date and time for sortable test fixtures, then copy any single ID, the full list, or just the encoded portion. The built-in decoder reverses the encoding and surfaces the embedded Unix-second value, the ISO 8601 string, the KSUID seconds (seconds since the KSUID epoch), the 16-byte random payload in lowercase hexadecimal, and the full 20-byte binary in hexadecimal, with exact error messages and the failing character index when a value is the wrong length, contains whitespace, or uses an alphabet character outside the base62 set. The Segment example KSUID, the all-zero nil KSUID, and the maximum representable KSUID are one click away as samples. Useful for debugging KSUIDs that show up in production logs, producing realistic seed data, comparing KSUIDs against UUID v4, UUID v7, ULID, NanoID, and Snowflake when choosing a primary key strategy, and shipping a quick test value into a Postgres or DynamoDB key column. Everything runs locally on your device; the KSUIDs you generate and any value you paste into the decoder never leave your browser.

Free to use. Works in your browser. No signup, no login.