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UUID Generator

Generate UUID v4 Identifiers and Random Hex with Full Randomness

Any developer who has hand-written an identifier generator knows the trap: timestamps collide, counters reset, and Math.random is not unique enough for distributed systems. This tool generates UUID v4 identifiers and random hex strings using crypto.getRandomValues, giving you 122 bits of pure randomness per identifier. That is enough entropy that generating a billion UUIDs per second for 85 years still leaves the odds of a collision at about fifty percent. Whether you need a database primary key, a client-side request ID, or a nonce for a test fixture, the tool produces standards-compliant output instantly.

How to Generate a UUID

  1. Click the generate button to produce a single UUID v4 in the standard 36-character format with hyphens.
  2. Use the batch option to generate multiple identifiers at once, ideal for seeding a database or creating fixtures.
  3. Switch to the random hex mode if you need a compact token without hyphens, such as a verification code or short link key.
  4. Choose a length for the hex output, from a few bytes up to a full 128-bit token.
  5. Copy the result with the copy button and paste it into your code, database, or configuration file.
  6. Verify the version and variant fields in the output, which mark it as a genuine v4 identifier, not a guess.

Example Input and Output

Imagine you are writing a migration script that inserts new rows into a users table. You need unique primary keys, so you generate UUIDs in batch mode. The output follows the v4 format exactly, with the version digit fixed at 4 and the variant bits in the right position.

InputOutput
generate 1 UUID v49f2c4e6a-1b3d-4f8e-9a2b-c5d6e7f8a9b0
random hex, 16 bytes4a9d1f3c7e2b8a5f6c0d3e9b1a7f2c4d

Tips for Using UUIDs Well

When to Use This Tool

Frequently Asked Questions

What is a UUID v4?

A universally unique identifier of 128 bits, where 122 bits come from a cryptographically secure random source. The remaining 6 bits encode the version (4) and the variant, which identify the format.

Can two generated UUIDs ever be the same?

In theory yes, but the probability is negligible. With 122 random bits, you would need to generate about 2.7 trillion IDs for a 50 percent chance of any collision, so duplicates are effectively impossible in practice.

Why does the fourth group always start with 4?

The version field is stored in that position. For v4, the value is fixed at 4 by the specification, which is how any system reading the UUID knows it was randomly generated.

Is this safe to use for security tokens?

Yes, because the source is crypto.getRandomValues, the same cryptographically secure generator browsers use for keys and sessions. Random hex from this tool is suitable for reset tokens and nonces.

What is the difference between UUID and random hex?

A UUID is a formatted 128-bit value with hyphens and version bits. Random hex is a raw string of hexadecimal digits with no structure, which makes it shorter and convenient for tokens and keys.

Should I use UUIDs as primary keys in my database?

They are a good choice for distributed systems and for merging data from multiple sources. For a single small database, an auto-increment integer is simpler and faster, so weigh your needs.

Are UUID v4 identifiers sortable by creation time?

No. Version 4 IDs are random, so they carry no time information. If you need time-ordered identifiers, use UUID v7 or a timestamp column alongside the UUID.

Does the tool work offline?

Yes. Generation uses the browser's built-in cryptographic functions, so no network request is made and no server is involved. The tool works even in a fully disconnected environment.

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