AI detectors
Grammarly's AI detector: how it works and what non-native writers should know
By ESL Humanizer editorial team · Checked September 2026
Short answer
Grammarly has a free AI detector on its website, and Grammarly Pro adds AI detection alongside plagiarism checks. Grammarly itself says no AI detector is 100% accurate and that detection shouldn't be used on its own — human writing, including non-native writing, can be flagged. Process evidence such as Grammarly Authorship is stronger than any score.
What Grammarly AI Detector is
A free web AI detector from Grammarly, with AI detection also built into Grammarly Pro.
| Checks for AI writing | Yes |
| Where it’s used | Individual writers and students checking their own text |
| Free access | Free AI detector on Grammarly's website |
| Paid | Grammarly Pro, from $12/month, adds AI and plagiarism detection in the editor |
What Grammarly AI Detector says about itself
Grammarly states that “no AI detector is 100% accurate” and that AI detection “should never be used as a standalone verification method.” See Grammarly AI Detector’s website for current details.
What independent research says
Vendor figures come from the vendor’s own tests. Independent research paints a more cautious picture of AI detection in general:
- In a peer-reviewed Stanford study, seven detectors misclassified an average of 61% of human-written TOEFL essays as AI-generated, while essays by US eighth-graders were classified almost perfectly (Liang et al., 2023).
- An independent test of 14 detection tools found none above 80% accuracy (Weber-Wulff et al., 2023).
- OpenAI withdrew its own AI classifier in 2023 for low accuracy (OpenAI).
What non-native writers should know
- Heavy use of Grammarly's own AI rewrites can itself change how detectors score your text.
- Authorship-style process evidence is more convincing than any detector result.
- If Grammarly flags your own text, fix unnatural phrasing rather than rewriting everything.
If Grammarly AI Detector flagged your work
- Check whether AI suggestions you accepted are what triggered the score.
- Keep a record of your writing process — Grammarly Authorship can help.
- Don't treat a self-check score as the verdict your school will reach.
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Quick answers
Does Grammarly have an AI detector?
Yes — Grammarly offers a free AI detector on its website, and Grammarly Pro includes AI detection alongside its plagiarism checker. Grammarly itself cautions that no detector is 100% accurate.
Will using Grammarly make my essay look like AI?
Spelling and grammar fixes are unlikely to. Accepting many full-sentence AI rewrites can make text more uniform, which some detectors score as more AI-like.