Does Grammarly Detect AI Writing? How Its Detector Works

Yes. Grammarly detects AI writing in two different ways: a statistical AI detector that scores pasted text, and Authorship, a provenance feature that records how text arrived in your document as you write it. The second one is the part most people miss, and it works nothing like Turnitin or GPTZero. It does not analyze your prose at all. It watches where the words came from.

That distinction decides how much a Grammarly AI result is worth, and what you can do about one. Here is what each feature actually measures, how reliable it is, and how Grammarly compares to the detectors schools and publishers use.

Does Grammarly detect AI writing?

It does, through an AI detection score in the Grammarly editor and through Grammarly Authorship, which logs whether each passage was typed, pasted, edited, or generated. The detection score behaves like other statistical detectors: paste text, get a percentage estimate of how much reads as AI-generated. Authorship is the more consequential feature, because it produces a report about the writing process rather than an opinion about the finished text.

Authorship only records sessions where Grammarly was actually running in the document. If you drafted somewhere else and pasted the result in, Authorship marks that block as pasted from an unknown source. It does not know what the source was. It only knows you did not type it there.

Does Grammarly detect AI like Turnitin?

No. Turnitin analyzes the submitted text statistically and returns a percentage; Grammarly Authorship tracks keystrokes and paste events while you write. They answer different questions. Turnitin asks whether this text looks machine-written. Authorship asks how this document came to exist.

Some instructors have started asking for an Authorship report alongside a submission, which is a meaningfully different demand from a Turnitin scan. It is a request for process evidence, and it is one of the few checks a humanizer cannot address, because the issue is not how the text reads.

Is Grammarly's AI detector accurate?

Its statistical score has the same ceiling as every other detector, and Grammarly presents it more cautiously than most competitors do. Statistical AI detection tops out around 85 to 95 percent on raw, unedited model output and falls off fast on edited or paraphrased writing, with false-positive rates on genuine human text running anywhere from 5 to 15 percent depending on the tool and the writer. Grammarly does not publish an independent benchmark that changes those bounds.

Authorship is a different question. As a record of what happened in the document it is reasonably reliable, but it is easy to misread. Pasting your own notes from a phone, moving a paragraph from an older draft, or dictating text can all show up as content you did not type in that session. A report full of paste events is not evidence of AI use, though it can look like it to someone who has not thought it through.

Does Grammarly detect AI plagiarism?

Plagiarism and AI detection are separate checks inside Grammarly. The plagiarism checker compares your text against web pages and academic databases to find matching passages. AI detection looks for machine-writing patterns in text that may be entirely original. AI-generated writing is usually not plagiarized in the traditional sense, which is exactly why institutions bought a second kind of scanner in the first place.

Both checks are on paid Grammarly plans. Neither one produces proof, and a document can come back clean on plagiarism while returning a high AI score, or the reverse.

Does Grammarly flag its own AI suggestions?

Yes, and this catches people out. Grammarly's own generative features write and rewrite text, and Authorship records that text as AI-generated in the document history, because that is literally what happened. Using Grammarly to improve a sentence is not the same as generating a paragraph, but the report distinguishes them less tidily than users expect. If an Authorship report is going to be shared, be deliberate about which of Grammarly's own AI tools you lean on while drafting.

Can Grammarly tell that a human edited AI text?

The statistical score responds to editing the way every detector does: real revision that varies sentence length and adds specific detail lowers the score. Authorship responds differently. Heavy editing of a pasted block shows as exactly that, a pasted block that was then worked on, which reads far better in a report than a single paste with no subsequent activity. Writers who care about the record tend to draft in the document rather than paste a finished piece into it.

What to do if Grammarly flags your writing as AI

If you wrote it, keep your evidence. Version history in Google Docs or Word shows a document that grew over time, and that timeline is stronger than any score in either direction. This is the same defense that works against a false positive from any detector, and it costs nothing to maintain.

If you drafted with AI and the writing genuinely reads mechanical, editing is the real fix. Vary your sentence lengths, cut the hedged phrasing, add specifics only you would know, and read it aloud. Those are the changes that lower a statistical score on Grammarly, GPTZero, and Turnitin at the same time, and they are what an AI content humanizer automates when you have a full draft to get through rather than a paragraph. The same principle applies well outside academia: the outreach sequences a sales team sends get ignored for the same reason flagged essays get flagged, a rhythm that reads generated.

What editing cannot fix is a provenance record. If someone asks for an Authorship report, the honest answer is to write in the document from the start. That distinction is the whole buying decision if you are weighing a paid tool, so we broke out all three Grammarly products, which of them a rewrite can move and what each costs, in the Grammarly AI detector and humanizer guide. The fourth product, the Grammarly AI humanizer, is the one people search for most and the one Grammarly is most careful about how it describes.

And if the reason you are here is that Turnitin is next and you are using Grammarly as a stand-in for it, that substitution only half works. The two models were trained separately and disagree routinely, though a high Grammarly reading is still real information worth acting on. We put the two side by side, including why Turnitin hides its own indicator below 20 percent, in Grammarly AI detector vs Turnitin.

One practical note for anyone working in Word or Google Docs rather than a text box: rewriting a full draft is a different job from fixing a paragraph, and humanizing a whole Word document keeps headings, lists, and terminology in place across every section.

Last updated July 2026. Grammarly ships feature changes frequently; check the current behavior of Authorship in your own account before relying on it.