UUID Generator

// A UUID v4 when you need an identifier now

A UUID is a 128-bit identifier that can be created without asking a central service for the next number. Version 4 is the random form most developers expect from a UUID generator. It fits database rows, API resources, fixtures, filenames, and any other place where separate systems need to mint identifiers independently.

This generator starts with one standard lowercase UUID v4 because that is the form most software accepts directly. Change the quantity for a newline-separated batch, then choose uppercase, remove the hyphens, wrap each value in braces, or add the urn:uuid prefix. Display changes keep the same underlying UUIDs, so reformatting a batch does not quietly replace it.

// Random in the browser, with the required bits set

Each value starts as 16 bytes from crypto.getRandomValues, the browser's cryptographic random source. The generator then sets the UUID version field to 4 and the variant field to the bit pattern required by RFC 9562. That leaves 122 random bits while keeping the familiar 8-4-4-4-12 hexadecimal layout.

Generation and formatting happen on your device. The UUIDs are not sent to a server or written to browser storage. A UUID is still an identifier, not a password or encryption key. If the value must grant access or protect data, generate purpose-built secret key material instead.

// fair questions

What version of UUID does this generate?

It generates UUID version 4, the random UUID form defined by RFC 9562. The version nibble is always 4, and the variant bits are set to the standard UUID layout.

Is a GUID different from a UUID?

GUID is the term commonly used in Microsoft tools and APIs for the same 128-bit identifier shape. The braces and uppercase options cover formats often seen in Windows and .NET code, while the underlying value remains a UUID v4.

Are these UUIDs guaranteed to be unique?

No random generator can promise an absolute absence of collisions. UUID v4 provides 122 random bits, which makes accidental collisions extremely unlikely when the cryptographic source works correctly, but applications should still enforce uniqueness where correctness depends on it.

Can I generate UUIDs in bulk?

Yes. Set the quantity from 1 to 1,000. Each UUID has its own Copy button, and a multi-value batch can be copied in one newline-separated block for fixtures, spreadsheets, or seed files.

Does changing the format generate a different UUID?

No. Standard, braces, compact, URN, lowercase, and uppercase are representations of the same generated value. Only the Generate button or a quantity change asks the browser for fresh random bytes.

Can I use a UUID as a password or API key?

Treat a UUID as a unique identifier, not as a general-purpose secret. Passwords, API credentials, encryption keys, salts, and nonces have their own requirements. Use a generator designed for that exact purpose when the value controls access or protects data.