UUID Generator v4

What this tool does

A UUID is a 128-bit identifier designed so that separate systems can create values that do not collide without asking a central authority. It is written as 32 hexadecimal characters in an 8-4-4-4-12 pattern, 36 characters including the hyphens.

Version 4 is the most widely used. It is generated from random data, with 122 random bits, which makes collisions a non-issue at any realistic scale. This tool uses the browser cryptographic random API, so the output contains no predictable pattern.

The practical advantage is that identifiers can be created on the client or on several servers at once without a round trip to the database, which suits distributed systems, offline-first applications, and architectures that merge data from multiple services.

When to use it

Use it to create unique keys for test data, to name files or trace requests, to obtain an identifier before a record is inserted, or to design a system where several services generate identifiers independently.

Input and output examples

Notes and limitations

Think about performance before using UUIDs as primary keys. Version 4 values are random and therefore unordered, so indexes do not grow sequentially and page splits become frequent; for insert-heavy tables consider a time-ordered alternative such as UUID v7 or ULID. Being hard to guess is also not an authorisation mechanism: access rights must still be checked separately.

Frequently asked questions