M-reader is a free online aid which enables teachers to verify that students doing extensive reading (ER) have understood graded reader books. This is achieved by students taking online quizzes. Established with the help of the Japanese Ministry of Education, M-reader is now used in 26 countries. Additive ER (extensive reading done outside class time) can only be widely used if effective measures are taken to ensure student accountability without overloading teachers or taking too much class time (Robb and Kano, 2013). M-reader satisfies these requirements, while recording the number of books and the number of words read.