About ULID Generator

Generate sortable ULIDs (Universally Unique Lexicographically Sortable IDs). Part of the DevTools Surf developer suite. Browse more tools in the Generators collection.

Use Cases

• Generating time-sortable primary keys for distributed databases
• Creating event IDs that naturally sort by creation time
• Replacing UUIDs in systems that benefit from lexicographic ordering
• Building audit logs with inherently chronological identifiers

Tips

• Generate multiple ULIDs at once for batch operations
• ULIDs sort lexicographically by creation time automatically
• Use ULIDs as database primary keys for time-ordered inserts

Fun Facts

• ULID was proposed by Alizain Feerasta in 2016 as a sortable alternative to UUID, encoding a 48-bit timestamp and 80 bits of randomness.
• ULIDs use Crockford's Base32 encoding (excluding I, L, O, U) to avoid ambiguity and offensive words in generated IDs.
• Unlike UUIDv4, ULIDs are monotonically sortable, meaning database indexes remain efficient without random page splits.

FAQ

What's a ULID vs a UUID?

ULID: 26-char Crockford base32, timestamp-prefixed, sortable by creation time, collision-free. UUID v4: 36-char hex, purely random. ULID is UUID v7's spiritual predecessor.

Is it cryptographically random?

The random portion yes (uses crypto.getRandomValues). The timestamp prefix is deterministic — same millisecond = same prefix.

When should I use ULID over UUID?

Databases where you insert and frequently sort by creation time. Index locality is much better with monotonic prefixes. For pure random IDs, UUID v4 is fine.

Does it work in Postgres/MongoDB?

Yes — ULIDs are lexicographically sortable as text, work as primary keys, and have libraries for every major database driver.