This extension prevents web pages from opening popup windows. All windows will get opened in the same window (in the currently active window). You can toggle the extension on and off from the toolbar button. When the extension is enabled, all windows are opened in the same active window. So if a website issues a popup window, instead the extension moves the newly created popup window into the active window and then focuses this newly created window (same as dragging a tab from one window to another window). When the extension is disabled, popup window opening is allowed. Note that this extension is not preventing other extensions from opening local popup windows.