ImageOptim - Faster web pages and apps.
OptiPNG - OptiPNG is a command-line PNG optimizer that recompresses image files to a smaller size, without...
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
TruePNG - Command-line PNG optimizer.
Oxipng - Oxipng is a multithreaded lossless PNG compression optimizer. It can be used via a command-line interface or as a library in other Rust programs.
pngquant - command-line utility and library for lossy compression of PNG images