Short Answer
No. Grammarly, spellcheck extensions, and any other grammar or writing-assistant software are not allowed during the Duolingo English Test. The test is measuring your unaided writing ability, so any tool that corrects or suggests text for you defeats the purpose — and the secure testing environment is specifically designed to detect and block it.
Why It's Blocked
The DET desktop app scans for active background software before you're allowed to begin. Browser extensions, grammar checkers, and similar tools running in the background can prevent your session from starting at all, or flag your test for review if detected mid-session.
What to Close Before You Start
- Grammarly and any similar writing-assistant browser extensions
- All open browser tabs and windows
- Remote-access or screen-sharing software
- VPNs — these cause immediate invalidation, not just a warning
How to Prepare Without It
Since you won't have grammar-checking support during the real test, the most useful practice is writing under the same conditions: no autocorrect crutches, a visible timer, and instant feedback afterward rather than in real time. That's exactly how Prepingo's writing drills work — you write unaided, then get detailed grammar and vocabulary feedback once your response is submitted.