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UUID Generator — RFC 4122 Version 4

Generate cryptographically secure UUID v4 identifiers using your browser's built-in random number generator. Choose uppercase or lowercase, with or without hyphens, and generate individually or in batches. Nothing is ever sent to a server.

00000000-0000-4000-8000-000000000000

About this tool

This tool generates version 4 UUIDs (Universally Unique Identifiers) as defined in RFC 4122, using your browser's crypto.getRandomValues API for cryptographically secure randomness. UUIDs are 128-bit identifiers that are statistically guaranteed to be unique across systems and time. You can choose uppercase or lowercase output, include or exclude hyphens, and generate a single UUID or a batch of five.

How to use

  1. A UUID is generated automatically when the page loads.
  2. Click the copy button to copy it, or the regenerate button to create a new one.
  3. Toggle uppercase and hyphens options to match your system's requirements.
  4. Click "Generate 5 UUIDs" to create a batch — each can be copied individually.

When to use this tool

  • Generating a unique identifier for a database record before writing code.
  • Creating UUIDs for test data or mock API responses during development.
  • Producing a unique key for a configuration entry, API token, or object ID.
  • Generating a non-sequential, non-guessable identifier for security-sensitive use cases.

Frequently asked questions

What makes a UUID unique?

122 bits of cryptographic randomness — approximately 5.3 × 10³⁶ possible values. The chance of a collision is negligible even across billions of generated IDs.

What is the difference between UUID v4 and other versions?

v1 uses timestamp and MAC address; v3/v5 use namespace hashing; v4 is purely random. v4 is most commonly used for general-purpose IDs because it exposes no system information.

Are these suitable as database primary keys?

Yes. UUID v4 is a common choice, especially in distributed systems where auto-increment integers would collide across multiple databases.

Is my UUID sent to a server?

No. All generation runs in your browser using crypto.getRandomValues. Nothing is transmitted.

Does this work offline?

Yes. Once the page has loaded, all generation runs locally.

What does "without hyphens" mean?

Removes the dashes from the standard UUID format, producing a compact 32-character hex string. Some systems prefer this form.

Can I generate multiple UUIDs at once?

Yes. Click "Generate 5 UUIDs" to create a batch with the current settings.

Is this tool free?

Yes, completely free with no sign-up required and no usage limits.

Generated locally using the browser's secure cryptographic API (crypto.getRandomValues) — no UUID is ever sent or stored on a server.