@bcoe, @domenic, I wonder if we need to start future proofing this now with an optional dictionary. Otherwise, in the future, we might have problems:

// An old browser would return a v4 uuid
// and the developer wouldn't know.
const uuid = crypto.randomUUID({ format: "v6" });

// They would need something not amazing like:

if (crypto.randomUUID.length) {
   // but you still don't know what versions are supported
}

If we added something like:

partial interface Crypto {
  [SecureContext] DOMString randomUUID(optional UUIDOptions options = {});
};

dictionary UUIDOptions  {
    UUIDFormat format = "v4"; 
 };

enum UUIDFormat { "v4" };

It also would allow developers to check if a particular format is supported.

try { 
  crypto.randomUUID({ format: "v3000" });
} catch {}

I think it remains pretty unlikely there will be another random UUID format that becomes widely used enough to be worth including, but I am not a domain expert.

Ok, I'll re-play this in #36... we can gather some options there.