UUID v4 Generator

About the UUID v4 Generator

This tool generates version 4 UUIDs entirely within your browser using crypto.randomUUID(), part of the Web Crypto API available in all modern browsers. No UUIDs are ever sent to or recorded by a server. Select how many you need (up to 100 at a time), toggle uppercase if required, and copy the results to your clipboard with one click.

What is a UUID?

A UUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier), is a 128-bit label standardised by RFC 4122. It is formatted as 32 hexadecimal digits displayed in five groups separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. UUIDs are designed to be unique across space and time without a central registration authority, making them ideal for distributed systems.

What is UUID v4?

UUID version 4 is generated using random or pseudo-random numbers. It is the most widely used UUID variant because it requires no coordination between machines and has an astronomically low collision probability — approximately 1 in 5.3 × 10³⁶. The 13th character is always 4 (version indicator), and the 17th character is always one of 8, 9, a, or b (variant indicator).

Common Uses for UUIDs

• Database primary keys — avoid sequential integer IDs that leak record counts and are hard to merge across databases.
• Distributed systems — generate IDs on any node without a central counter, enabling offline-first and multi-region architectures.
• File and asset naming — give uploaded files unique names to prevent collisions and avoid exposing original filenames.
• Session and correlation tokens — track requests across microservices or log aggregation systems.
• Testing and seeding — generate realistic-looking IDs for test fixtures and database seeds.