The Facial Action Coding System

The Facial Action Coding System (FACS) is a tool used to categorize and describe every recognizable facial movement by analyzing specific muscle actions. Developed by psychologists, it breaks down facial expressions into individual muscle movements called Action Units (AUs). By observing these AUs, FACS provides a detailed map of facial expressions, helping to interpret emotions, reactions, or communication cues. It’s used in research, security, healthcare, and AI to better understand the subtle signals our faces convey, offering a systematic, objective way to analyze facial behavior across various contexts.