UUID v4 Generator, private by default

What UUID v4 values are for

A UUID is a 128-bit identifier commonly written as five groups of hexadecimal characters. Version 4 UUIDs are random, which makes them useful when you need identifiers that are unlikely to collide without coordinating with a central sequence.

Developers use UUIDs in database records, mock data, API examples, webhook payloads, distributed systems, local test fixtures, and temporary objects where a simple incremental number would be too predictable or too easy to collide.

Random does not mean secret

A UUID v4 is designed to be unique enough for identifiers, not to act as a password, API key, session token, or proof of authorization. Treat UUIDs as IDs unless your application adds separate access controls.

If a URL contains a UUID, anyone with the URL may still be able to access the resource unless the backend verifies permissions.

• Use UUIDs for identifiers, fixtures, and references
• Use generated passwords or proper tokens for authentication
• Use access checks even when IDs are hard to guess
• Avoid exposing private records just because their IDs are random-looking

Practical developer workflow

Choose a batch size, generate UUIDs, and copy the values into test data, migrations, API examples, or QA notes. Keep hyphens for standard display unless a system specifically asks for compact UUIDs.

Because generation happens in the browser, this tool is fast and useful even for local notes or private fixtures that do not need to leave your device.