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.
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.
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 also what reduces false flags. 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.