An EXS file is an instrument used by Logic Pro, a digital audio workstation (DAW). It contains an instrument, which includes information referenced by Logic to play an audio sample according to its type, such as a piano, guitar, or drums.

EXS files are used by EXS24, a sampler library that comes included with Logic Pro X. The library contains a large collection of samples such as strings, brass, synth textures, and pianos. EXS24 can be used to arrange sounds you recorded yourself or that were already recorded to be played back from a MIDI track within Logic or from your MIDI keyboard. EXS files are located in the "Sampler Instruments" and the "EXS Factory Samples" folders in the "Logic" folder on your hard drive. A "Samples" folder is also located in the "Logic" folder and it contains audio files, such as .WAV or .AIF files, that are referenced by Logic when playing the associated EXS file. You can add EXS instruments to these folders, which will then appear in the instruments menu in Logic. If Logic is open when you add the instrument you need to refresh the menu in order for the instrument to appear.