According to IFABC Global Web Standards, a unique user (UU) is "An IP address plus a further identifier. The term "unique visitor" may be used instead of "unique user" but both terms have essentially the same meaning (see below). Sites may use User Agent, Cookie and/or Registration ID." Note that where users are allocated IP addresses dynamically (for example by dial-up Internet service providers), this definition may overstate or understate the real number of individual users concerned.