How is a ULID different from a UUID?

ULIDs are 26 characters, case-insensitive in canonical form, and start with a timestamp component so sorts match creation order. UUID v4 is unordered; UUID v7 is similar in intent with a different encoding.

Why Crockford base32?

It avoids ambiguous characters (O/I/L) and stays compact for URLs, headers, and filenames while remaining human-transcribable.

Are ULIDs unique across machines?

Randomness after the timestamp makes collisions extraordinarily rare. Still follow your datastore guidance if you need global uniqueness proofs beyond the spec.

Do ULIDs leak exact timestamps?

The first characters encode millisecond time. Do not use ULIDs as hidden credentials; treat them like public correlation IDs.

Can databases index ULIDs efficiently?

Monotonic prefixes reduce index fragmentation versus random UUID v4, though extremely high insert rates still benefit from tuning strategies.

How do ULIDs compare to UUID v7?

Both target sortable uniqueness. Choose ULID when you want shorter strings; choose UUID v7 when your stack already standardizes on UUID columns.

Is generation offline?

Yes — values are minted locally in the browser.

Can I convert ULID to binary?

Libraries in your language can decode the 128-bit structure; this tool focuses on canonical string generation.

ULID Generator

Generate Live

Generate sortable, URL-safe ULID identifiers.

About this tool

ULID Generator — Generate sortable, URL-safe ULID identifiers. Free, fast and private. Runs entirely in your browser at Quick Calci Tools.

Examples

Common scenarios for the ULID Generator.

Single ULID

26-character uppercase Crockford string (e.g. 01ARZ3NDEKTSV4RRFFQ69G5FAV).

Bulk for events

count: 50

50 lexicographically sortable IDs for an ingest pipeline.

Who uses the ULID Generator?

Common scenarios and audiences for this tool.

Backend engineers

Issue correlation IDs that sort in distributed logs without a centralized snowflake service.

Mobile developers

Create offline-first IDs shorter than hex UUIDs for URL sharing and QR payloads.

Data platform teams

Seed bronze-layer tables where lexicographic ordering simplifies incremental merges.

SRE & tracing

Stamp spans and canary deployments with identifiers humans can grep quickly.

API designers

Expose opaque resource tokens that remain URL-safe without percent-encoding.

Frequently asked questions

Everything you need to know about the ULID Generator.