FileOptimizer is not available for Mac but there are plenty of alternatives that runs on macOS with similar functionality. The best Mac alternative is Caesium Image Compressor, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 25 alternatives to FileOptimizer and 15 are available for Mac so hopefully you can find a suitable replacement. Other interesting Mac alternatives to FileOptimizer are ImageOptim (Free Personal, Open Source), E-mage (Free, Open Source), JPEG Archive (Free, Open Source) and UPX (Free, Open Source).
Caesium Image Compressor lets you compress your pictures up to 90% without visible quality loss. Providing a simple yet effective interface with a real-time preview and multiple image processing at the same time, everyone will be able to reach the best result.
ImageOptim is excellent for publishing images on the web (easily shrinks images “Saved for Web” in Photoshop). It's useful for making Mac and iPhone/iPad applications smaller (if you configure Xcode to allow better optimization).
Utilities for archiving photos for saving to long term storage or serving over the web. The goals are: use a common, well supported format (JPEG), minimize storage space and cost, identify duplicates / similar photos.
UPX (Ultimate Packer for eXecutables) achieves an excellent compression ratio and offers very fast decompression. Your executables suffer no memory overhead or other drawbacks for most of the formats supported, because of in-place decompression.
Leanify is a lightweight lossless file minifier/optimizer. It removes unnecessary data (debug information, comments, metadata, etc.) and recompress the file to reduce file size. It will not reduce image quality at all. Features
Crunch - Insane(ly slow but wicked good) PNG image optimization. It combines selective bit depth, color type, and color palette reduction with zopfli DEFLATE compression algorithm encoding using embedded versions of the pngquant and zopflipng PNG optimization tools.