What are some alternatives?
ImageKit.io - Instant multi-platform image optimization
Crunch - Crunch is an OS X tool for PNG image file optimization.
Shrink Me - Compress images with one drag / click
Piio - Generates responsive images so you don't have to optimize
Landscape by Sprout Social - An interactive tool for social media image resizing
Compress for macOS - Dramatically compress JPG and PNG Images, convert PSD to JPG