There are many applications available to optimize images; we'll be using ImageOptim as it's free and open source.
Note
ImageOptim analyzes each image and determines the most efficient algorithm, or best way, to compress the content, then removes any unnecessary comments or color profiles. ImageOptim is lossless, so our images won't lose any quality.
1. Download ImageOptim from http://imageoptim.pornel.net.
2. Extract the downloaded file by double-clicking on it. Drag the application to your application folder.
3. Open ImageOptim.
4. Drag your images onto the table in the app; it'll automatically optimize and save each one. You can drag multiple images at a time or an entire folder, and ImageOptim will process them all and display the saving.
5. Your images are now optimized! You can see the savings you make...