Most people know Grammarly as the tool that fixes commas and tightens sentences. So it surprises students to learn that Grammarly now also has an AI-detection feature. Does it actually work, and does it matter for your grade? Here's an honest breakdown of what Grammarly can and can't tell you about AI writing.
Grammarly is a writing assistant first
It's worth starting here, because it frames everything else. Grammarly's core job is to help you write — grammar, spelling, clarity, tone, and increasingly, AI-powered rewriting and generation. Detection is a newer, secondary feature bolted onto that mission. That's different from a tool like Turnitin, whose whole purpose is integrity checking. So when you ask "does Grammarly detect AI," the answer is yes, but it's not what the product is built around.
Yes, Grammarly has an AI-detection feature
Grammarly has added AI-detection capabilities, including an "AI text" flag that estimates how much of a document appears to be AI-generated. Paste or write text, and it can give you a read on how machine-like the writing looks. Like other detectors, this is an estimate based on patterns — how predictable and uniform the text is — not a measurement of who actually typed it. We explain that pattern-matching in how AI detectors work.
The irony: Grammarly's own AI can affect detection
Here's the twist worth pausing on. Grammarly also offers AI suggestions and generative rewriting. If you accept a lot of those suggestions — or use Grammarly to generate or heavily rewrite text — you're introducing AI-shaped patterns into your writing. That same machine-smoothed phrasing is exactly what AI detectors, including Grammarly's own flag, are tuned to notice. So the tool that helps you write can, in some cases, nudge your text toward looking more "AI" to a detector. It's not a conspiracy, just a natural consequence of how these systems work.
How reliable is Grammarly's detection?
About as reliable as detectors in general — which is to say, imperfect. The honest picture:
- It can flag obvious AI text that's smooth and generic.
- It produces false positives, flagging clean human writing, just like every other detector.
- It misses edited or mixed text.
- It's weakest on short passages.
No detector is 100% accurate, and Grammarly's is no exception. Treat its AI reading as a rough signal, not a verdict. For the bigger picture on detector reliability, see do AI detectors actually work?
Grammarly is not what schools run for misconduct
This is the most important practical point. When your instructor "checks for AI," they're almost certainly not pasting your essay into Grammarly. Institutions typically use integrity tools built into their submission systems — most commonly Turnitin's AI indicator, covered in does Turnitin detect ChatGPT? So a clean Grammarly result doesn't guarantee your school's detector will agree, and a Grammarly flag doesn't mean you're in trouble with your institution. They're different tools with different training and different quirks.
Grammarly's "Authorship" feature is a different, more useful signal
Separate from the AI-detection flag, Grammarly also offers a feature called Authorship, and it's worth knowing the difference. Instead of guessing from patterns after the fact, Authorship is opt-in process tracking: turn it on before you start writing in the Grammarly Editor, Google Docs, or Microsoft Word, and it logs how the document actually came together — keystrokes typed, text pasted from a website, text taken from a non-web source, and any Grammarly or AI suggestions you accepted. The output is a color-coded report, and even a replay of the document from first draft to final edit, that an instructor can look through to see where each sentence came from.
That makes it a meaningfully different kind of evidence than a detector score. A Turnitin or Grammarly AI percentage is an inference about the finished text; an Authorship report is a record of the process that produced it — closer to the "keep your drafts and version history" advice we give in does Turnitin detect ChatGPT?, just built into the writing tool itself. Some instructors now accept an Authorship report in place of, or alongside, a detector score, precisely because it shows work rather than estimating it.
The catch: it only works if you turn it on before you write, so it can't retroactively vouch for a document you've already finished without it, and plenty of schools still haven't adopted it as accepted evidence at all. It also documents process, not quality or honesty by itself — a fully tracked report proves you typed the words, not that you didn't lean on an AI tool off-screen for ideas you then typed yourself. It's a useful option to know about, not a substitute for following your school's actual AI policy.
How to use Grammarly sensibly
Grammarly is genuinely useful — for its actual job. Reasonable use looks like:
- Fixing grammar, spelling, and clarity on writing that's yours.
- Getting a rough, free gut-check on how AI-like a passage reads.
- Being aware that leaning hard on its generative rewrites can make your text read more machine-like.
Check your institution's academic-integrity policy on AI, since the rules differ by school, department and assignment, and following them is your responsibility. If your school bans AI on an assignment, using Grammarly's generative features to produce the work and disguising it is still dishonest — no tool changes that. Where polishing legitimately helps is making your own draft read naturally instead of flat, which is simply better writing. If honest writing keeps getting flagged, why is my writing flagged as AI? explains why.
The bottom line
Grammarly does detect AI writing now, via an "AI text" flag, but it's a secondary feature on a writing assistant — not the misconduct tool your school runs, and not more accurate than detectors in general. Use it for what it's good at, remember its own AI suggestions can shift how your text reads, and don't treat its result as proof either way.
Questions people ask
Does Grammarly detect AI writing?
Yes. Grammarly has added an AI-detection feature and an "AI text" flag that estimates how much of a document looks AI-generated. Like all detectors, it's an estimate based on patterns, not proof of who wrote the text.
Is Grammarly what my school uses to catch AI?
Almost certainly not. Schools typically use integrity tools built into their submission systems, most commonly Turnitin's AI indicator. A Grammarly result doesn't necessarily match what your institution's detector reports.
Can using Grammarly make my writing look more like AI?
It can. If you accept lots of Grammarly's AI suggestions or use its generative rewriting, you introduce machine-smoothed phrasing, which is exactly the kind of pattern detectors are tuned to flag.
What is Grammarly Authorship, and is it the same as the AI-detection flag?
No. The AI-detection flag estimates whether finished text looks machine-written. Authorship is a separate, opt-in feature that logs how a document was actually written — typed text, pasted text, and accepted AI suggestions — as a report you can share. It has to be turned on before you start writing, and it documents process, not proof of honesty by itself.