Williams DNA project is a useful site to help the many, many Williams narrow in on their particular Williams line, at least for those in the USA, but only if you have a male Williams relative descended paternally from a Williams line who is willing to provide a DNA sample, and either pay for it or allow you to pay for it. Strongly recommend springing for at least the 25 marker test, and 37 is even better. Anything shorter probably won't provide a strong enough link to a Williams group to be useful to you.

Williams is the 3rd most common surname in the country and it can be very easy to go barking up the wrong tree. The more Williams who participate the more useful this site will be. YDNA is not a substitute for genealogical research, but can help confirm or refute the some of the assumptions and theories researchers often make to try to fill in the significant gaps in documentation that nearly always are present, and which has led more than one researcher down the wrong path.