Photosensitivity is a prevalent condition in which visual stimuli, such as flashing lights, trigger seizures or other adverse reactions. Videos are common sources of these unsafe stimuli, and although there are efforts to reduce certain types of strobing, the range of problematic stimuli is broad, unpredictable, and difficult to filter against. The inventors have developed a method to actively detect and modify harmful stimuli in videos, thereby protecting photosensitive individuals from exposure. Importantly, this method can protect viewers against a wide range of problematic stimuli without degradation of video quality. This invention has broad consumer and business applications to ensure a safe visual environment for all photosensitive individuals.