UTF-16 is the only web-encoding incompatible with ASCII,[3] and never gained popularity on the web, where it is used by under 0.005% (less than 1 hundredth of 1 percent) of web pages.[4] UTF-8, by comparison, is used by 97% of all web pages.[5] The Web Hypertext Application Technology Working Group (WHATWG) considers UTF-8 "the mandatory encoding for all [text]" and that for security reasons browser applications should not use UTF-16.[6]