Does Grammarly Get Flagged as AI?

It is a genuinely worrying discovery. You wrote every word yourself, ran it through Grammarly the way you always have, and the AI score came back high.

The short version is that this is real, it has a boring technical explanation, and it is not evidence that you did anything wrong. But it is worth understanding properly, because the explanation is also the thing you would say if someone asked you about it.

Grammarly does not generate your text, but it does change its statistics

Detectors do not look for fingerprints left by particular software. There aren't any, and no detector has a list of which tools touched your document.

What they measure is perplexity — how surprised a language model is by each word in your text. Writing where every word is the expected one scores low, and low perplexity is read as machine-written, because language models generate by repeatedly choosing likely words.

Now consider what an editing tool does. It finds the awkward construction and suggests the conventional one. It replaces the unusual word with the standard one. It smooths the sentence that did not quite work into one that does.

Every one of those changes moves your prose toward the statistical centre. That is not a side effect — it is the entire function. And the statistical centre is exactly where detectors expect machine writing to sit.

So the tool that makes your writing more correct also makes it more predictable, and predictability is what the score reports.

This is the same mechanism that hits second-language writers

Worth connecting, because it explains why the effect is uneven.

The writers most affected by this are the ones who use editing tools most heavily, and that skews toward people writing in a second language — who already score higher for an unrelated reason. A smaller active vocabulary means safer, more common word choices, which lowers perplexity before any tool is involved.

Published research found detectors misclassify non-native English writing at dramatically higher rates. Add heavy grammar-tool use on top and the effect compounds. The mechanism is set out in why AI detectors fail non-native English speakers.

The uncomfortable summary: the people doing the most to write correctly are the ones most likely to be flagged for it.

Which Grammarly features actually matter

Not all of it moves the needle equally, and the distinction matters for both detection and policy.

Spelling and grammar corrections. Fixing a misspelling, a subject-verb disagreement, or a missing article changes almost nothing statistically. These are mechanical corrections of errors, and they are permitted essentially everywhere. Nobody has ever been disciplined for spellcheck.

Clarity and conciseness rewrites. Suggestions that restructure a sentence rather than correct it. These change more, because they replace your construction with a more conventional one. Still usually permitted as editing, but this is where the statistical effect begins.

Tone and fluency rewriting. Larger rewrites that change register. More impact on the score, and more likely to be addressed explicitly by an institutional policy.

Generative features. Grammarly now offers text generation. This is a different thing entirely — not editing your sentence but writing one — and most policies that address AI treat it as AI use. If you use it, that is the tier where disclosure obligations start.

The line worth holding in your head: a tool that corrects your sentence is editing; a tool that writes one is generating. The first is assistance, the second is substitution.

What to do if your score is high

Do not panic, and do not rewrite the work. A detector score is not a finding. Turnitin's own guidance to institutions states its AI indicator should not be the sole basis for a misconduct decision, and altering flagged work afterwards is the single worst move available — it looks like concealment and it creates a discrepancy between what you submitted and what you defend.

Keep your version history. If you draft in Google Docs, the timeline showing the document being built over sessions is far stronger evidence than any score is against you. This is worth setting up before you ever need it — the full method is in how to keep a writing audit trail.

Be ready to explain the mechanism. Not "the detector is wrong," which reads as deflection, but: detectors measure predictability rather than authorship, and grammar tools reduce predictability by design. An assessor who understands that usually stops treating the number as evidence.

Check what your policy actually says. Many institutions permit language support explicitly, and some now state that a detector score alone cannot support a finding. Both are useful sentences to be able to quote. Our guide to which tools count as language support covers how to read a policy.

If you are already facing an accusation, the full sequence is in falsely accused of using AI, with adaptable wording in appeal letter templates.

Should you stop using it?

No, and the reasoning matters more than the answer.

Writing worse to satisfy a broken measurement is a bad trade in every direction. Your writing gets worse. The skill you are building gets distorted. And you are surrendering a legitimate tool because of a number that carries no authority on its own and that most policies explicitly say cannot stand alone.

There is a version of this worth doing, and it is different. If you want writing that is both better and less predictable, build the thing the metric was a poor proxy for: vocabulary range, deliberate variation in sentence length, and the willingness to use your own phrasing rather than the smoothest suggestion.

That means accepting some of Grammarly's suggestions and declining others. When it offers a more conventional word and your own was clearer or more precise, keep yours. The tool is advisory, not authoritative, and treating every suggestion as a correction is how prose gets sanded down to the average.

Our guides to sentence rhythm and finding your writing voice cover the mechanics of building that range deliberately.

The wider point

Grammarly is not being detected. Nothing is detecting Grammarly. What is happening is that a tool designed to make writing conventional is being measured by a system that treats conventional writing as suspicious.

That is a flaw in the measurement, not in the tool or in you. It will not be fixed by writing badly, and it should not be treated as a reason to stop using help that genuinely improves your work.

Keep the drafts, keep the tool, and know the explanation. That is the whole defence, and it is a good one.