This colourless salt is a popular photographic developer used in monochrome photography.

[3] Being an electron-rich arene, metol is readily degraded by hydrogen peroxide.

This combination is very versatile; by varying the quantities of Metol, hydroquinone, and restrainer, and adjusting the pH, the entire range of continuous tone developers can be made.

The exact composition of Bogisch and Hauff's early Metol is unknown, but it was most likely methylated at the ortho position of the benzene ring (p-amino-o-methylphenol), rather than at the amino group.

Because it has been in use for this purpose for over 100 years, and often by amateur photographers, there is a substantial body of evidence regarding the health problems that contact with Metol can cause.