M-reader is a free Internet site which helps educational institutions to manage extensive reading (ER). It enables teachers to verify that students have read and understood graded reader books. This is achieved by students taking online quizzes designed to test their understanding of a book’s plot and characters, rather than how well they remember the book. Teachers and students can easily track the number of books and the number of words read. M-reader, established with the help of research funds from Kyoto Sangyo University in Japan and the Japanese Ministry of Education, was first made available online in March 2013 and is now used by educational institutions in 26 countries. In numerous contexts, teachers would like to conduct additive ER (extensive reading done outside of class time). Additive ER can only be widely used if effective measures are taken to ensure student accountability without overloading teachers or taking too much class time. M-reader meets these conditions.