Why does Task Manager disappear briefly when you switch it into or out of Always on top?

Raymond Chen

If you go to Task Manager’s Options menu and toggle Always on top, the Task Manager window disappears briefly, and then returns. What’s the reason for this?

When Task Manager goes into Always on top mode, it’s doing more than just being an always-on-top window in the WS_EX_TOPMOST sense. Because WS_EX_TOPMOST isn’t good enough any more.

Windows 8 introduced the concept of windows existing beyond the normal plane of existence. Windows 8 apps, the Start screen, toast notifications, and the lock screen (among other things) all exist in their own world outside those of regular Win32 desktop apps.

An always on top Task Manager wants to get in on that action. Otherwise, your Task Manager that’s marked Always on top would nevertheless get covered by Windows 8 apps and the Start screen.

When you switch into or out of Always on top mode, Task Manager launches a new copy of itself into the alternate universe, and the exits the previous instance. That’s the reason for Task Manager disappearing briefly: The old copy is gone, but the new copy has yet to arrive.

You can observe the effects of this switcheroo by watching the process ID in (ironically) Task Manager. The process ID of taskman.exe will change when you switch into or out of Always on top mode.