The proxy icon is the little icon located in the center of an application's document window. Any app that creates a document you can store on your Mac will have a proxy icon in the window's title; this includes text editors, word processors, spreadsheets, and image editors.
The proxy icon has been around since OS X was first introduced. But many of us have no idea what its function is, or even where it is. Without further ado, let's meet the proxy icon.
What Is the Proxy Icon in OS X?
The proxy icon is a small icon located in an application's window. It represents the document you're currently working on. The proxy icon is usually centered in an application's document window, and is located above any toolbar that may be present. Its function is to serve as a proxy for the document you're working on. In essence, the icon acts as if it's the actual document icon you would find using the Finder.
What Can I Do With the Proxy Icon?
Well, since it represents the actual document file you're working with, you can use the proxy icon in much the same way you would use a file in the Finder. For instance, you can drag the proxy icon to your desktop or to a Finder window. Doing so will move the current document to whatever location you chose.
Additionally, you can:
Option-drag: Create a copy of the proxy icon instead of moving it when you drag it to a new location.
Command, Control, or Right-Click: Display the current path to the document you're working on. In addition, if you click on any folder along the displayed path, a Finder window will open for that folder.
Does the Proxy Icon Always Work Like this?
It should, though each third-party application developer can choose to implement the proxy icon slightly differently, or not at all. There is also one often-overlooked issue with the proxy icon. It won't work until you have saved the document. After all, it's a proxy to a file on your Mac. If you're working with a new document you haven't saved yet, the proxy icon won't do anything.