Mirrors is a remake of a 2003 South Korean horror film, Geoul sokeuro (2003) [Into the Mirror]. Geoul sokeuro was written and directed by South Korean film-maker Sung-ho Kim. It was adapted for Mirrors by French filmmaker Alexandre Aja, who also directed this film.
In order to obtain an r-rating the theatrical version had to be cut slightly. Only violent scenes were altered. The unrated version includes those scenes which were cut before. Both versions have been released on the same DVD in the USA.