UUID / ULID

UUID / ULID Generator

Generate UUID v4 or ULID identifiers in bulk.

Generate UUID v4 or ULID identifiers in bulk.

Type

How many

All values are generated locally in your browser.

Include hyphens

Turn off to get a compact UUID string.

Uppercase output

Convert all characters to uppercase.

Generated values

Click any row to copy it.

Generate to see results here.

What

UUID / ULID Generator definition

A UUID is a 128-bit identifier designed to be globally unique.

Cases

Use Cases

Generate IDs for database records

Create request or trace IDs

Seed test data with unique values

How To

How to Generate UUID or ULID

A step-by-step guide to creating unique identifiers quickly.

Select type

Choose between UUID v4 or ULID.

Set quantity

Enter how many IDs to generate (1–100).

Generate and copy

Click Generate, then click a row or Copy all.

Knowledge

Understanding Unique Identifiers

What is a UUID?

UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122. When properly generated, UUIDs are practically unique across all systems without central coordination.

UUID Versions

UUID v1 uses timestamp and MAC address. UUID v4 is completely random (most common). UUID v5 uses namespace and name hashing. Each version has different uniqueness guarantees and use cases.

What is ULID?

ULID (Universally Unique Lexicographically Sortable Identifier) combines a 48-bit timestamp with 80 bits of randomness. ULIDs are time-sortable (unlike UUIDs) and URL-safe (no hyphens or special characters).

Collision Probability

With 122 random bits (UUID v4), you'd need to generate 2.71 quintillion UUIDs to have a 50% chance of collision. In practice, collisions are astronomically unlikely for any reasonable scale.

Storage Considerations

UUIDs can be stored as: strings (36 chars with hyphens), compact strings (32 chars), or binary (16 bytes). Binary storage saves space and improves index performance in databases.

FAQ

UUID / ULID generator FAQ

When should I use UUID v4 vs ULID?

UUID v4 is random; ULID stays time-sortable while remaining unique.

Are generated IDs unique and local?

Values are generated in the browser with no network calls; collisions are extremely unlikely.

Why toggle hyphens or uppercase?

Hyphenless or uppercase variants help with compact storage or case-insensitive systems.

How do I keep IDs stable across runs?

Use a deterministic generator (not provided here) when you need repeatable IDs; this tool always produces random values.

How did UUIDs originate?

UUIDs were standardized in RFC 4122 (2005), building on DCE GUIDs to provide globally unique identifiers without coordination.

How popular are UUIDs and ULIDs?

UUID v4 is widely supported across languages and databases; ULID has grown for systems needing sortable IDs while staying URL-safe.

What are common UUID/ULID use cases?

Database primary keys, distributed events, object storage keys, and correlation IDs in logs or traces.

Any maintenance tips for identifiers?

Store IDs as binary where supported for performance, validate expected version/length, and avoid exposing sequential IDs when privacy matters.

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UUID / ULID Generator