The Complete Guide to Using Custom Icons in OS X

Use a Mac long enough and you’ll eventually stumble upon forums like the “Post Your Desktop” threads at sites like MacRumors. Mac users love to customize the look and feel of OS X, and one of the easiest ways to do it is by using custom icons for your apps and utilities.
Apps like CandyBar have long offered a quick solution to managing your Mac’s application icons, but it’s just as simple to change most icons yourself. Here’s an overview on how to use custom icons in OS X.

Standard Apps

OS X includes a number of “special” applications (e.g., Calendar, Finder, Trash) that need some specific attention when it comes to changing their icons, and we’ll discuss those more below. For most apps, though, the process is fairly straightforward.
First, identify the app you want to modify and find a suitable replacement icon. In our example, we’ll change the icon for iTunes in our OS X Mavericks installation to the Yosemite iTunes icon teased by Apple during WWDC. You can use practically any JPEG or PNG image file as an icon, but you’ll see the best results with uniformly sized PNGs with transparency. Great places to find replacement icons that are properly formatted include deviantART and the MacRumors forums.
Download the image you’d like to use as your new icon and open it in Preview. With the image open and Preview the active application, press Command-C to copy the entire image.
Next, find the original location of your app (not it’s Dock or Desktop shortcut). For almost all applications, you’ll find the correct file in your Applications folder, located at Macintosh HD/Applications. In our iTunes example, the iTunes.app file is found in the top level Applications folder. If you want to change the icon of a system utility like Activity Monitor or Terminal, you’ll find these apps in the Utilities subfolder of the Applications folder.
Quit the app if it’s running and then highlight it in Finder. Press Command-I to open the Get Info window. Alternatively, you can right-click on the application and select “Get Info.”

Here, click on the small application icon preview at the top of the window, to the left of the application name (not the larger icon preview at the bottom of the window). You’ll see the icon preview outlined in blue once you’ve correctly selected it.

Now press Command-V to paste the image you copied earlier. You’ll see both icon previews change to display the new icon, and you can close the Get Info window if you’re satisfied with the new look.

If you don’t like the way that the new icon looks, you can press Command-Z to undo the change, or highlight the small preview icon at the top of the window and press Delete to revert to the default icon.

Once you’ve made your changes, the new icon will be displayed in Finder or via Desktop shortcuts. To get your new icon to show up on the Dock, either quit and relaunch the app or head to Terminal and enter the following, case-sensitive command:

killall Dock

Repeat this process for each app icon you wish to modify and you’ll soon have a slick custom Dock. Now, what about those special apps we mentioned earlier? We’ll show you how to change the icons for Finder, Calendar, and Trash on the next page.

How to Change the Finder Icon in OS X

The Finder is one of the “special” apps mentioned earlier, and it requires a different approach for changing its icon. Most custom Finder icons you download will include two PNG files: finder.png and finder@2x.png.
We need to place these files in a specific location within OS X’s Dock support files. Navigate to Macintosh HD/System/Library/CoreServices. Here, find the file called Dock.app, right-click, and choose Show Package Contents.

This will take you inside the Dock’s package file structure. From here, navigate to Dock.app/Contents/Resources. Here you’ll find the default finder.png and finder@2x.png files. Be sure to make a backup copy of these two files in case you wish to revert your Finder icon back to the default in the future. Unlike standard app icons, you can’t undo or delete the new Finder icon without replacing these files again.
Once you’re all set, copy the new icons into the Resources folder, choosing to overwrite the existing files when prompted. As we’re modifying a system file here, you’ll need to enter an administrator’s password to complete the operation.
As before, use the killall Dock command in Terminal to reload the Dock and see the new Finder icon. In some cases, however, you may have to reboot in order to see the change.

How to Change the Calendar Icon in OS X

OS X’s Calendar app (iCal in earlier versions of OS X) is another unique app that requires some special steps to change its icon. This is due to the live update feature that lets the app display the current date in its Dock icon.
Similar to custom Finder icons, any properly formatted Calendar icon you download will include two .icns files: App-empty.icns and App.icns. If you’re working with PNG files, you can use an app like Img2icns to convert PNGs to .icns files.
Once you have your custom App-empty and App icon files, quit Calendar if it’s open and then locate the Calendar.app file in the Applications folder. Right-click and select Show Package Contents and then continue navigating to Calendar.app/Contents/Resources. Here, you’ll find the original App-empty and App files. As recommended with Finder, make backup copies of these files in case you ever wish to restore the default icon.

When you’re ready, copy your new files into the Resources folder, choose to overwrite the existing files, and enter your administrator’s password if prompted.
But wait! We’re not yet done. There’s still one more file we need to replace. In the Resources folder, find Calendar.docktileplugin. Open it, and navigate to Contents/Resources. Here, you’ll find another App-empty.icns file. Copy your custom App-empty file here, too, and once again overwrite the existing file.
Quit and relaunch Calendar, or use the killall Dock Terminal command to see the new Calendar icon show up on your Dock.

How to Change the Trash Icon

Yes, you can even customize the Dock Trash Can in OS X. In our example, we’ll be using the new Trash icon from the OS X Yosemite developer builds.
Once again, you’ll need to replace multiple files for the Trash icon, accounting for both empty and full designs in both standard and Retina 2X resolutions. The Trash icon files are located in the same folder as the Finder icons:

Macintosh HD/System/Library/CoreServices/Dock.app/Contents/Resources

Remember to right-click on Dock.app and choose Show Package Contents in order to continue navigating past that point. Here, you’ll find four files that you need to replace:

• trashempty.png
• trashempty@2x.png
• trashfull.png
• trashfull@2x.png

Most custom Trash icons you download will include these four files. If you’re working with custom images, simply format and name your files appropriately.

Make backup copies of the original files in case you wish to revert to the default Trash icon in the future. Then copy your custom Trash icons into the Resources folder, choose to overwrite the existing files, and enter your Admin password. Again, head to Terminal and use the killall Dock command to reset the Dock and see your new Trash icon in action.

Where to Find Custom OS X Icons

As mentioned earlier, OS X lets you use almost any PNG or JPEG image file as a custom icon, but if you’re artistically challenged like us, you’ll want to utilize some of the thousands of beautifully designed custom icons made by talented Apple fans from all over the world. Here’s a list of some of our favorite sites for finding cool new OS X icons.

• deviantART
• MacRumors “Flat Icons” Thread
• InterfaceLIFT
• Iconfactory

Let us know in the comments if you have additional resources we should include.
Featured image via AlienValley/deviantART