No need for complex design software and moving pixels around, Image2icon automatically crafts icons that fit your needs. Image2icon is a wonderful tool for making custom icons right on your Mac. You’ll not only need to convert your png or jpg to an icon format, you’ll probably also have to tweak the size, resolution, and more. Let’s say you have an image or a screenshot and you want it to be an app icon. However, 99% of app icon customization problems arise when you have to pick the right icon format. Your macOS has the feature that allows you to do that. The process of changing an app icon is quite simple and doesn’t require any special tools. In this article, we guide you through the process of changing icon (Mac, iPhone, and iPad), as well as explain how to turn images to icons, transfer icons across devices, and a few more useful things. Even more, you can create your own icon from an image and use it for any app. Alternatively, you can use a tool such as OnyX and check IconServicesunder Cleaning > User to clear the cache.Luckily, there are ways to replace new app icons with the old ones.Even a reboot doesn't make the new icons appear in Finder (though it does appear in other contexts such as in the Dock), but there are two workarounds: either (a) move the bundle to a different folder, or (b) rename the bundle given that reverting to the original path and name makes the problem reappear, you'd have to plan ahead: create your bundle in a different location or with a different name, then move / rename to the desired location / name.As others have noted, there are icon caching issues, which can be tricky to resolve as of OSX 10.10.4:.Thus, for instance, you'd need a script to put the updated icons in place programmatically every time the bundle is saved. Any changes to AutomatorApplet.icns are lost whenever you modify and re-save the bundle in Automator.Percent 20's answer is more comprehensive and portable in principle, but comes with two caveats: the icon displayed by the bundle itself, such as when showing an alert, is still the original icon.For instance, you cannot store a custom icon in a Git repository. relies on extended attributes of the HFS+ filesystem, which are lost when copying the bundle to a filesystem that doesn't support them.The accepted answer works in principle, but:

To complement the existing, helpful answers:

Mac icon sets icns