When you're ready to take the test, your test session should be the only thing running on your computer. Before you start the test, close programs including all browsers (Chrome, Firefox, etc.), telecommunication software (Skype, Discord, etc.), remote desktop software (Teamviewer, Anydesk, etc.), and spelling or grammar checkers (Grammarly, etc.). You can also double check that there aren’t any programs running in the background without you knowing.
For Mac users: Do this by right-clicking on the application icons and selecting the "quit" option.
For Windows users: Do this by quitting all programs, then going to the system tray/notification area and closing every program that is visible.
If in doubt, you can shut down your computer entirely and only launch the Duolingo English Test desktop application. In addition to passing a security check, this also helps ensure you have a stable test experience!
Watch this video for more information about closing external programs before taking the test. In addition, the video below walks through closing background programs in the Windows system tray/notification area.