ImageOptim - Faster web pages and apps.
OptiPNG - OptiPNG is a command-line PNG optimizer that recompresses image files to a smaller size, without...
pngquant - command-line utility and library for lossy compression of PNG images
pngCrushrrr - Drag your PNGs onto PNGCrushrrr and get super-optimized files ready to be emailed or posted on the...
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
pngcrush - Pngcrush is an optimizer for PNG (Portable Network Graphics) files.