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ULID Generator

Generate sortable, timestamp-based ULID identifiers as an alternative to random UUIDs.

Guide

Interactive workspace

No account required
ULID Generator
Batch generate

Time prefixes sort by creation millisecond. With Monotonic on, random tails within the same millisecond increment instead of being random, so the batch stays strictly sortable.

Decode / validate a ULID

Paste any ULID to check it and read the timestamp embedded in its first 10 characters.

A ULID is 26 Crockford Base32 characters: the first 10 encode a 48-bit millisecond timestamp, the last 16 encode 80 bits of randomness — so ULIDs sort in creation order as plain strings. Generation happens locally in your browser with crypto-grade randomness.

How to use it

  1. Select Generate new ULID.
  2. For multiple values, expand Batch generate and set the count.
  3. Generate the list and copy it; treat the leading time component as public information.
What is ULID Generator?

Generate sortable, timestamp-based ULID identifiers as an alternative to random UUIDs.

How it works

SiteIndex encodes the current timestamp and cryptographically random bytes using Crockford's Base32 alphabet to produce a 26-character ULID that sorts naturally by creation time.

Common uses
  • Generate identifiers that sort chronologically in a database index.
  • Replace random UUIDs where insertion order matters for performance.
  • Generate a batch of test identifiers for seed data.
Limitations
  • The timestamp comes from the device clock. IDs generated in the same millisecond have random tails, not guaranteed monotonic order.
  • An identifier is not a password, access token, or uniqueness guarantee.
Frequently asked questions
How is a ULID different from a UUID?
A ULID encodes a millisecond timestamp in its first 10 characters, so ULIDs generated later always sort after earlier ones, unlike random UUIDs.

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