 <p>You are probably talking of a borderless <code>NSWindow</code> (<code>NSBorderlessWindowMask</code>), with an opaque background view whose alpha is set to zero and an <code>NSProgressIndicator</code> subview to show the progress. You also probably want to use the <code>-[NSWindow center]</code> method to nicely center your window.</p> <p>However, I doubt that you want that kind of UI. A progress bar is probably not visible on top of all desktops, and thus aesthetically worthless.</p> <p>I think a rounded, half-transparant black window will be more suited in your case. Take a look at <a href="http://mattgemmell.com/source/#roundedfloatingpanel" rel="nofollow">Matt Gemmell's source code</a>.</p>