# ULID Generator

Canonical URL: https://offlineutils.com/ulid-generator
Category: Developer
Published: 2026-06-24
Publisher: offlineutils.com
Runs entirely in the browser; nothing entered into the tool is uploaded.

> A ULID Generator produces Universally Unique Lexicographically Sortable Identifiers — 128-bit identifiers encoded as 26 Crockford base32 characters, sorted by time and safer for URL use than UUIDs — using the browser's CSPRNG with zero network traffic.

ULIDs encode a 48-bit millisecond timestamp followed by 80 bits of randomness in a single 26-character string. They're case-insensitive, URL-safe, monotonically increasing within the same millisecond when generated together, and lexicographically sortable. Pick a quantity, toggle uppercase, and copy or download the list. The generator uses crypto.getRandomValues for the random portion.

## Features

- Generate up to 1,000 ULIDs (128-bit, 26-char Crockford base32) at a time
- 48-bit ms timestamp + 80 bits of CSPRNG randomness
- Monotonic mode for guaranteed sortability within the same millisecond
- Uppercase / lowercase toggle
- Bulk copy as a newline-delimited list or JSON array

## Use cases

- Primary keys that stay close on disk for B-tree-friendly insert performance
- Time-ordered event IDs for audit logs and ledgers
- URL-safe identifiers that double-click-select cleanly
- Replacing UUID v4 keys in a schema you can still freely migrate

## How to use it

1. **Pick a quantity** — Enter how many ULIDs you need (1 to 1,000).
2. **Toggle monotonic mode** — On by default — guarantees lexicographic ordering even within a single millisecond.
3. **Copy the list** — Click Copy to grab the entire batch as newline-delimited text.

## When to use it, and when to use something else

- **vs UUID v4** — use ULID Generator when you want time-ordered, lexicographically sortable IDs friendly to B-tree indexes. Use UUID v4 when you specifically want no timestamp leak in the ID.
- **vs Snowflake / KSUID** — use ULID Generator when you want a widely-supported standard with no server coordination. Use Snowflake / KSUID when you need a coordinator-assigned ID that strictly orders across nodes.

## Frequently asked questions

### How is a ULID different from a UUID?

Both are 128 bits. ULIDs encode 48 bits of timestamp + 80 bits of randomness in a 26-char string that's lexicographically sortable, while UUID v4 is fully random. ULIDs are nicer for primary keys because sequential inserts stay close on disk.

### Are ULIDs safe to expose in URLs?

Yes — Crockford base32 deliberately omits ambiguous characters (I, L, O, U), so ULIDs are URL-safe, case-insensitive, and double-click-selectable.

### Will two ULIDs ever collide?

Within a single millisecond, 80 bits of randomness mean the collision probability is astronomically low. Across milliseconds, the timestamp prefix differs, so collisions are effectively impossible.

## Related tools

- https://offlineutils.com/uuid-generator
- https://offlineutils.com/timestamp-converter
- https://offlineutils.com/hash-generator