What are some alternatives?
Lepton - Lepton image compression: saving 22% losslessly from images at 15MB/s
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
File Converter - Convert & compress everything in 2 clicks!
JPEGmini - JPEGmini - The Photo Optimization Tool Trusted by Tens of Thousands Image Perfectionists
ImageOptim - Faster web pages and apps.
CodeKit - CodeKit allows you to optimize the performance of your website by automatically and efficiently compiling a variety of popular languages.