Squash
Squash is a native, high-performance macOS application for bulk compressing, resizing, and converting images.
Offline Compression
HandBrake
HandBrake is an open-source, GPL-licensed, multiplatform, multithreaded video transcoder. It's a tool for converting video from nearly any format to a selection of modern, widely supported codecs.
ImageOptim
A free app that makes images load faster and take less disk space, without sacrificing quality. Removes private EXIF data from photos and improves compression.
Optimage
The 1st tool for automatic image optimization at consistent image quality, with the highest compression ratio and performance.