You can find any PNG icon online (as long as it’s square and high-resolution) and make it an icon for any app, file, or folder on your Mac.Īfter you download the PNG icon, double-click the image to open it in the Preview app. When it comes to icons of any sort, PNG, with its transparent background, is the most popular format out there. Change App, File, and Folder Icons Using PNG Images Here are the two most popular methods for changing icons on Mac. If you want to keep things interesting, try changing the icons of your favorite apps, files, and folders. The default Mac desktop gets boring after a while.