Generate v4 UUIDs using your browser's cryptographic random source, one at a time or a hundred at once, in the casing and format you need.
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Version 4 UUIDs — 122 random bits from your browser's cryptographic random source.
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Each identifier is produced on your device and is never recorded anywhere.
UUID Generator uses your browser’s cryptographic random source and never sends or stores what it produces.
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A version 4 UUID is a 128-bit identifier of which 122 bits are random; the other six mark it as version 4 and as conforming to the RFC 4122 variant. Nothing coordinates them, which is the point — two machines that have never met can both mint identifiers without a central authority and without colliding.
The probability of a collision is small enough to ignore in practice: you would need to generate billions of UUIDs before it became worth thinking about. What that guarantee rests on entirely is the quality of the randomness.
So the randomness here comes from your browser's cryptographic random source — crypto.randomUUID where it exists, crypto.getRandomValues where it does not — and from nowhere else. There is no fallback to Math.random, which is predictable and unsuitable; if no secure source is available the tool refuses to generate rather than quietly producing weaker identifiers that look exactly the same.
Generate one or a hundred at a time, in whichever form your target expects: hyphenated, compact, brace-wrapped for a Windows GUID, or prefixed as a URN. Changing the format re-renders the identifiers you already have rather than replacing them, so you can settle the casing without losing the batch.
They come from your browser's cryptographic random source, the same one used for keys and session identifiers. There is no fallback to Math.random — if that source is unavailable, the tool reports an error instead of generating anything.
Negligible. With 122 random bits you would need to generate on the order of a billion UUIDs per second for decades before a collision became likely.
The UUID is generated from random data, as opposed to version 1, which encodes a timestamp and a MAC address, or version 5, which hashes a name within a namespace. Version 4 is the right default when you just need an identifier that is unique.
No. A v4 UUID is unpredictable, but it is designed to be shared, stored and logged, and it is not a credential. Use a purpose-built token for anything that grants access.
UUIDs are case-insensitive, and the RFC recommends generating them in lowercase. Uppercase is offered because some systems, Windows GUIDs in particular, conventionally display them that way.
No. They are generated in your browser and exist only on this page until you copy them. Nothing is transmitted, recorded or retained.
