Does Grammarly trigger AI detection?

Turnitin's own FAQ, reproduced across university support pages, states that its detector is not tuned to target Grammarly-generated spelling, grammar and punctuation modifications, and that in tests on human-written documents, changes made by Grammarly free and premium were in most cases not flagged.

Turnitin's chief product officer, Annie Chechitelli, told EdSurge in 2024 that in the company's internal testing traditional grammar-checking tools do not set off its alarms.

So fixing a comma splice, correcting a misspelling, or tightening an awkward clause is not what the detector is looking for. It is looking for text whose statistical shape resembles language-model output.

Turnitin is equally explicit about the exception. Its FAQ says that content generated by Grammarly's generative AI-powered features — including draft generation, paraphrasing, summarising and similar — will likely be flagged as AI-generated.

That is consistent rather than contradictory. A paraphrasing tool rewrites your sentence into a new one chosen by a model, and the resulting prose carries the statistical regularity a detector measures. The detector cannot tell which product produced it and does not need to: it is reading the output, not tracking the tool.

If you used Grammarly to rewrite paragraphs, generate a draft, or summarise a source, expect that to register.

Between those two cases sits heavy, bulk acceptance of suggestions. Students and instructors have reported papers being flagged after a writer accepted a very large number of Grammarly recommendations, and news coverage has described such cases.

These are accounts rather than measured data, and we have not seen a controlled study of it. The mechanism is plausible, though: accept enough rewording and the prose drifts toward the smoothed, even register that detectors read as machine-like — not because Grammarly is generative, but because the result is less variable than how you actually write.

The practical reading is that light correction is safe on the record available, wholesale rewriting is not, and there is a middle where nobody can give you a firm answer.

In the same 2024 interview, Chechitelli said something more revealing than any accuracy claim: “We probably let about 15 percent of bot-written text go by unflagged. We would rather turn down our accuracy than increase our false-positive rate.”

That is a deliberate design choice, and an honest one. But it tells you what a detector score is: a tuned tradeoff between missing real AI use and wrongly accusing real students, set by a vendor. It is not a measurement of authorship, and it was never built to be.

Use Grammarly for what it was originally for — correcting your own sentences — and be deliberate about its generative features in work that will be checked. If a paraphrasing suggestion rewrites your meaning rather than your punctuation, you are into the territory Turnitin says it flags.

Keep your drafts regardless. Version history in Google Docs or Word shows your work developing over time, and that is far stronger evidence of authorship than any score is evidence against it. Turnitin itself states it does not determine misconduct; it provides data for educators to interpret under their own policies.

And do not try to write badly on purpose to look more human. It does not reliably work, it makes your writing worse, and it looks far worse if it ever comes up.