TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
ImageOptim - Faster web pages and apps.
TinyJPG - Compress JPEG images with perfect quality and file size
Caesium Image Compressor - Compress your pictures up to 90% without visible quality loss.
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.
TheImageKIT - TheImagekit - One stop Platform offering most popular image operations in magically simple way. Completely FREE.