Duplicate Windows visually copies any window in Mac OS X live and on-the-fly. It’s like display mirroring for individual windows! I created the tool to display windows across multiple monitors in extended desktop mode during presentations. It’s proven useful to watch web videos over other windows as demonstrated below, or to keep an eye on windows I’m not actively using. I’m certain that there are yet undiscovered uses for such Duplicate Windows. Features and Operation Duplicate Windows lets you select from among all window objects known to the operating system. Once you select a window, the new copy changes its size to match the window you’ve asked it to copy. When you resize the new window, it maintains the aspect ratio of the source window. The new copy keeps itself up-to-date fast enough to keep up with just about anything, from video to fast animation. Mouse clicks and key presses on the copy are not forwarded to the original, and so far the program does not work across spaces. Duplicate Windows is capable of copying a window that is actively playing video, though not without some slight artifacts. I’ve found that these are not too distracting for personal use, but may not be professional enough for some uses. Duplicate Windows fails to render windows that are across Spaces, or windows that are minimized. The list of windows available to duplicate includes the menu bar, all the UI services icons (the small icons on the right side of the Menu Bar), and many other things you may not have known were windows. This is a little confusing at first, but technically necessary to provide maximal flexibility to the tool.