Software & Apps File Types What Is an ICNS File? How to open, edit, and convert ICNS files by Tim Fisher General Manager, VP, Lifewire.com Tim Fisher has 30+ years' professional technology support experience. He writes troubleshooting content and is the General Manager of Lifewire. our editorial process Facebook Twitter LinkedIn Tim Fisher Updated on June 22, 2020 File Types Design Cryptocurrency MS Office Windows Linux Google Drive Apps File Types Backup & Utilities View More Tweet Share Email A file with the ICNS file extension is a macOS Icon Resource file (often referred to as the Apple Icon Image format) that macOS applications use to customize how their icons appear in Finder and in the OS X dock. They're equivalent in most ways to the ICO files used in Windows. An application package typically stores the ICNS files in its /Contents/Resources/ folder and references the files within the application's Mac OS X Property List (.PLIST) file. ICNS files can store one or more images within the same file and are normally created from a PNG file. The icon format supports the following sizes: 16x16, 32x32, 48x48, 128x128, 256x256, 512x512, and 1024x1024 pixels. How to Open an ICNS File ICNS files can be opened with Folder Icon X and the Apple Preview program in macOS. Adobe Photoshop can open and build these files but only if you have the IconBuilder plugin installed. Windows can open ICNS files using Inkscape and XnView (which can both be used on a Mac as well). IconWorkshop should support the Apple Icon Image format on Windows, too. Considering that this is an image format, and several programs support opening it, it's possible you'll find that one program on your computer is configured by default to open ICNS files but you'd prefer a different one do the job. If you're using Windows, and you'd like to change which program opens it by default, learn how to change file associations. How to Convert an ICNS File Windows users should be able to use Inkscape or XnView to convert the ICNS file to basically any other image format. If you're on a Mac, the program Snap Converter can save the file as something else. Regardless of the operating system you're on, you can also convert an ICNS file with an online converter like CoolUtils.com, which supports output formats like JPG, BMP, GIF, ICO, PNG, and PDF. To do this, just upload the file to the website and choose which format to save it in. Alternatively, if you want to create an ICNS file from a PNG file, you can do so quickly on any OS with the iConvert Icons website. Otherwise, we recommend using the Icon Composer tool that's part the Apple Developer Tools software suite. Still Can't Open the File? If your file isn't opening properly with these programs, look at the file's extension again to confirm that you're not misreading it. Some files might at first appear to use this extension when really it's just spelled similarly. ICS is one example. It's a very similar looking, and very common, extension but has nothing to do with ICNS icon files. Your file might instead be an InCopy Document Preset file that uses the ICST file extension. If so, you need Adobe InCopy on your computer to view it.