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Free UUID Generator

Generate random version-4 UUIDs — one at a time or in bulk — and copy them with a click. They’re created with secure randomness in your browser.

Quick answer

A UUID (universally unique identifier) is a 128-bit value written as 32 hexadecimal digits in the pattern 8-4-4-4-12, such as 3f2504e0-4f89-41d3-9a0c-0305e82c3301. This tool generates version-4 UUIDs, which are random, using cryptographically secure randomness, so the chance of two generated UUIDs colliding is vanishingly small (negligible in practice).

Formula & method

Each UUID is generated using the browser’s cryptographically secure random source (crypto.randomUUID where available, otherwise crypto.getRandomValues). The result is a version-4 UUID: 122 of its 128 bits are random, with the version and variant bits set to fixed values. Generation is local — nothing is sent anywhere.

Examples

Example 1: A single UUID
Input
Generate one
Result
3f2504e0-4f89-41d3-9a0c-0305e82c3301
Why
32 hex digits grouped 8-4-4-4-12; the “4” marks version 4.
Example 2: Bulk generation
Input
Generate 100
Result
100 unique UUIDs, ready to copy
Why
Useful for seeding test data or IDs.
Example 3: Version digit
Input
Any v4 UUID
Result
Third group starts with 4
Why
The version-4 marker is always the first digit of the third group.

When to use this tool

  • Creating unique IDs for database rows, files, or test fixtures.
  • Generating correlation IDs for logs or requests.
  • Anywhere you need a unique value without a central counter.

Common mistakes

  • Assuming UUIDs are sequential or sortable. Version-4 UUIDs are random, not time-ordered.
  • Treating a UUID as a secret. It’s an identifier, not a security token.
  • Worrying about collisions. With 122 random bits, duplicates are astronomically unlikely.

Frequently asked questions

What is a UUID?

A universally unique identifier — a 128-bit value shown as 32 hex digits in the 8-4-4-4-12 pattern. It’s designed so that independently generated IDs don’t clash.

What is a version-4 UUID?

A UUID whose bits are mostly random. 122 bits are random and a few are fixed to mark the version (4) and variant. It needs no central authority to generate.

How likely are two UUIDs to collide?

Vanishingly unlikely. With 122 random bits, you’d need to generate billions per second for many years before a collision became probable.

Are these UUIDs cryptographically random?

Yes. They use the browser’s secure random source, so they’re suitable as unpredictable identifiers — though a UUID is an identifier, not a password.

Are the UUIDs uploaded anywhere?

No. They’re generated in your browser and never sent to a server.

Can I use a UUID as a password?

A UUID is a valid string of characters, so yes. However, UUIDs are 36 characters (including hyphens) and predictable in structure (not random entropy), so a dedicated password generator is generally better for security-critical use.

What if I generate the same UUID twice?

It's extremely unlikely. With 122 random bits, the odds are astronomically small: you would have to generate about a billion UUIDs per second for roughly 85 years to reach even a 50% chance of a single collision. You can safely assume each generated UUID is unique.

Sources & references

External references open in a new tab. We are independent and not affiliated with these organizations.

  • ✓ Free to use
  • ✓ No sign-up required
  • ✓ Runs entirely in your browser — nothing is uploaded.
  • ✓ Formula and method shown above
Last updated: How we calculateReport a correctionDisclaimer

Provided “as is” for general information only — results may be inaccurate, so verify before you rely on them. No warranty; use at your own risk.

Built and reviewed by HIFreeTools against the formula shown above and any authoritative references cited on this page. See our methodology and editorial standards.

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