GibbonFACS is a modification of the original human FACS system (Ekman & Friesen 1978), for use with hylobatid species (gibbons and siamangs) and was established following the same methods used in the development of ChimpFACS, MaqFACS, OrangFACS, DogFACS and CatFACS.

The resulting GibbonFACS Manual is an additional, freely available tool for scientists interested in comparative communication research, supporting already existing facial action coding systems to studying facial expressions.