HIFreeTools

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 collisions are effectively impossible.

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.

  • ✓ 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.

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