About: The Equine Facial Action Coding System (EquiFACS) is an observational tool for identifying and recording facial movements in horses. The system is based on the facial anatomy of horses and has been adapted from the original FACS system, which was developed to record human facial movements. EquiFACS provides a comprehensive list of all the facial movements that horses can produce, which can be used to document facial expressions across a wide range of contexts. The EquiFACS manual details how to use the system and code the facial movements of horses objectively and reliably. This has recently been published in the peer reviewed journal, PLOS One, and is freely available to all.