Introduction: Most Invalidations Are Honest Mistakes
An invalidated Duolingo English Test (DET) means you lose your test fee and have to retake the exam from scratch. It's easy to assume this only happens to people who tried to cheat, but in practice most invalidations come from candidates who broke a proctoring rule without realizing it. Four mistakes account for the large majority of "Not Certified" results. This guide walks through each one plainly, without guessing at exact thresholds Duolingo hasn't published, so you know what's actually safe and what isn't.
Table of Contents
- Don't Run Other Apps or Background Programs
- Don't Look Away From Your Screen
- Don't Let Outside Voices Reach Your Microphone
- Don't Let Your Secondary Camera Move
- What to Do If Your Test Was Not Certified
1. Don't Run Other Apps or Background Programs
The DET desktop app should be the only program running on your computer during the test. Before you start, close every browser, messaging app (WhatsApp, Slack), call/streaming app (Zoom, Discord, Twitch, Spotify), and remote-access tool (TeamViewer, AnyDesk). On Windows, check the system tray and Task Manager; on Mac, right-click each dock icon and choose Quit. Taking the test on a virtual machine is not allowed.
Does a browser open in the background count?
Yes. Even if you're not actively using it, a browser running in the background counts as another program. Close it before you begin.
2. Don't Look Away From Your Screen
The DET's proctoring system uses webcam-based eye and head tracking to confirm you're engaged with the test rather than consulting outside material. Duolingo hasn't published an exact "seconds" threshold, so treat any guide (including older versions of this one) that states a precise cutoff as an estimate, not an official rule. The safest approach is simple: keep your eyes on the screen, especially during speaking tasks.
Is it okay to look down at my keyboard while typing?
Yes. Glancing down to type is a normal part of using a computer and isn't treated as looking away.
What counts as "looking away" during a speaking task?
Looking up, to the side, or down for an extended period while you're supposed to be speaking can register as disengagement. If you need a moment to think, pause and keep looking forward at the screen rather than looking away.
Will one quick glance invalidate my test?
A brief, natural glance is generally not a problem on its own. It's sustained or repeated looking away — particularly during scored speaking and writing tasks — that tends to trigger a review.
3. Don't Let Outside Voices Reach Your Microphone
The DET's audio monitoring listens for voices other than your own during the test. This includes another person talking in the room, a TV or video playing nearby, or a phone call in the background. Test in a room by yourself, tell people you live with that you're testing, and mute or silence anything that could produce unexpected sound.
What if someone else in my home makes noise accidentally?
Isolated background noise doesn't automatically mean invalidation, but a clearly audible second voice can be flagged for human review. Minimize the risk by testing in a closed room and warning others in advance.
Can I use noise-cancelling headphones?
Check Duolingo's current official equipment rules before your test, since permitted hardware can change between test releases — this is worth confirming directly on the official DET site rather than assuming last year's rule still applies.
4. Don't Let Your Secondary Camera Move
Since the secondary phone-camera requirement was introduced, the camera must keep your full screen and keyboard visible for the entire test. If it shifts and that view is lost, the session can be invalidated. Lean the phone against something solid, position it horizontally, and place it on a stable, flat surface. Turn on Do Not Disturb so a call or notification doesn't disrupt the setup.
For a full walkthrough of the current secondary-camera requirement and common setup mistakes, see our dedicated second-camera setup guide.
What if my phone moves slightly during the test?
Reposition it right away if you notice it's shifted, and keep going — stopping the test yourself is generally worse than a brief camera adjustment.
5. What to Do If Your Test Was Not Certified
These four areas account for most invalidations. If your result still comes back as "Not Certified," you're not necessarily out of options. Our step-by-step appeal guide walks through how the appeal process works and how to submit one.