Spitfish is a free de esser VST, Audio Unit plugin developed by digitalfishphones. Compatible OS(s): Windows 64b, macOS.
Spitfish is a dead-easy to use de-esser, aimed mainly at mono or stereo vocal tracks. Just like classic analog de-essers, this unit dynamically filters out harsh, annoying s-like sounds that would otherwise ‘spit’ in your face.
http://www.digitalfishphones.com/