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ULIDs (Universally Unique Lexicographically Sortable Identifiers) solve a problem UUIDs don't: they encode a timestamp directly into the identifier, so ULIDs generated later always sort after ones generated earlier — useful for database primary keys where insertion order matters. This generator creates one or more valid ULIDs on demand, each a 26-character, URL-safe, sortable identifier.
How it works
Choose how many ULIDs to generate. Each ULID encodes the current Unix timestamp in milliseconds as the first 10 characters, followed by 16 characters of cryptographically random data, all encoded in Crockford's Base32 alphabet.
- Enter number of ULIDs to generate.
- Click Calculate to see your results.
Examples
A generated ULID
A ULID looks like "01ARZ3NDEKTSV4RRFFQ69G5FAV" — 26 characters, with the leading portion encoding the creation timestamp.
Who should use it
- Generating primary keys for a database table where chronological sort order matters.
- Creating unique, sortable identifiers for distributed systems or event logs.
Industry applications
- Software engineering and database design
- Distributed systems and event sourcing
Advantages
- Naturally sortable by creation time, unlike random UUIDs.
- More compact and case-insensitive compared to a standard UUID string.
Limitations
- The embedded timestamp reveals approximately when the identifier was created, which may not be desirable for all use cases.
Common mistakes to avoid
- Treating a ULID's timestamp portion as fully hidden — it does reveal the approximate creation time to anyone who decodes it.
- Mixing ULID and UUID formats in the same database column without normalizing to one format.
Best practices
- Use ULIDs for primary keys where you want both uniqueness and natural chronological sort order without a separate timestamp column.
Tips
- If you need many ULIDs generated within the same millisecond, remember that only the random portion differs between them — sort order for same-millisecond ULIDs falls back to that random suffix.