This article was previously published under Q205158
Sometimes, it might be necessary for an application to prevent its main window from appearing on the taskbar. This article describes two ways that this can be accomplished.
There are two ways to prevent a window from appearing on the shell's taskbar and in the task list window that appears when you press ALT+TAB.
Give the window the WS_EX_TOOLWINDOW extended style, and remove the WS_EX_APPWINDOW style. As a side effect, the window will have a smaller caption than a normal window.
Give the window the WS_POPUP style and make it owned by a hidden window.
If a window is created or shown such that it appears in the taskbar, then the window should be in the same state when it is destroyed or hidden. If the visibility on the taskbar is not synchronized, then the taskbar may end up with a blank button where it thinks the window should still appear.