On Windows, you have the ability to use multiple desktops to organize your applications. Starting with version 144, when a link is opened from an external application, Firefox will only use windows that are on the current desktop. If there are no such windows, it will open a new window on that desktop.

You can configure behaviors related to desktops by making changes in the Configuration Editor:

To return to the old behavior where, when a link is opened from an external application, Firefox will use the most recently used window regardless of what desktop it's on, set the widget.prefer_windows_on_current_virtual_desktop preference to false.

Additionally, when restoring a previous session, by default Firefox will restore windows to the desktop they were last on (if that desktop still exists). To disable this behavior and instead have all windows be restored to the current virtual desktop, set the browser.sessionstore.restore_windows_to_virtual_desktop preference to false.

WARNING from the moderator team: Changing Firefox preferences from the about:config page can sometimes break Firefox or cause strange behavior. You should only do this if you know what you're doing. Please read Firefox advanced customization and configuration options to learn more.