What is an ICNS File?

How to Open, Edit, & Convert ICNS Files

ICNS Files
ICNS Files Used in Inkscape.

A file with the ICNS file extension is a Macintosh OS X 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.

ICNS files are 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 the Apple Preview program in macOS, as well as with Icon Machine and Folder Icon X. Adobe Photoshop can open and build ICNS 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.

Tip: If your ICNS file isn't opening properly with these programs, you might look at the file's extension again to confirm that you're not misreading it. Some files may look like ICNS files but they're really just using a similarly named file extension. ICS, for example, is a very similarly named, and very common, extension but has nothing to do with ICNS icon files.

If none of these suggestions above are helping you open your ICNS file, it's possible that a different file format utilizes this same extension, in which case you'll need to do some digging into that specific ICNS file to see what to do next. One way to do this is to open the file as a text document in Notepad++ to see if there's any readable text within the file that gives away what format it's in or what program was used to create it.

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 the ICNS format by default, see my How to Change File Associations in Windows for instructions.

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 be used to save the ICNS file as something else.

Regardless of the operating system, you're on, you can also convert an ICNS file with an online image converter like CoolUtils.com, which supports converting the ICNS file to JPG, BMP, GIF, ICO, PNG, and PDF. To do this, just upload the ICNS file to the website and choose which output 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, I recommend using the Icon Composer tool that's part the Apple Developer Tools software suite.

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