Bleaching means whitening or oxidizing a substance. A bleach is a chemical that can produce these effects. Common chemical bleaches include sodium hypochlorite, or "chlorine bleach," and "oxygen bleach," which contains hydrogen peroxide. "Bleaching powder" is calcium hypochlorite. Bleaching can be a preliminary step in the process of dyeing.

A bleaching agent, or bleach, is any compound that bleaches the colour out of fabrics, paper, or other materials. Household bleach or sodium hypochlorite is used in the home for whitening clothes, removing stains, and disinfecting. This is because sodium hypochlorite yields chlorine radicals, oxidizing agents readily reacting with many substances. Hair bleach contains H2O2 (hydrogen peroxide), which gives off oxygen radicals as it decomposes. Oxygen and chlorine radicals both have comparable, and excessive bleaching effects.Chlorine bleach is commonly used as a disinfectant by homemakers and janitors. Mixing bleach and cleaners containing ammonia can create toxic chloramine gases and a nasty explosive called nitrogen trichloride.