Grammarly's AI detector: how a writing assistant judges its own users
Grammarly's AI detector is unusual because of where it sits. It is known for being tied to Grammarly's writing assistant and its authorship features, which aim to show how a document was written: typed, pasted, or generated. So the same product that suggests rewrites also reports whether the result looks generated. Humanize 360 approaches this from the writer's side: a grammar checker that explains every fix rather than rewriting for you, and a detector that shows the eleven signals a rewrite tends to disturb.
To be clear about limits: no tool can promise what Grammarly's detector will report, and its result on a paragraph will not match GPTZero's or Turnitin's. According to its public documentation it estimates how much of a text appears AI-generated and is meant as guidance for the writer rather than as a verdict for a reader. What follows is about the habits that push writing toward a machine-shaped result, and how to keep your own voice while still using an assistant.
A detector inside a writing assistant
Grammarly checks grammar, tone and clarity as you type, offers full-sentence rewrites, and can draft text on request. Its detector reports an estimate of AI-generated content, and its authorship tools can record how text entered a document. The interesting consequence is that a person who writes every word themselves but accepts every clarity suggestion can end up with text the same product estimates as partly generated. That is not a contradiction. Suggestions come from a model, and model-shaped sentences look like model output.
Accepting every suggestion makes writing uniform
- Clarity rewrites shorten long sentences and lengthen fragments, pushing everything toward a medium length. Sentence-length variance falls.
- Tone suggestions replace casual phrasing with standard business phrasing. Stock-phrase density and transition-word overuse rise.
- Formality settings remove contractions. Contraction rate drops to zero, which reads as machine text to most classifiers.
- Word-choice suggestions swap your slightly odd word for the expected one. Perplexity falls with every swap.
Keeping your voice while using an assistant
Use the assistant for what it is good at: spelling, agreement, punctuation, the errors that are simply wrong. Decline the rewrites that change rhythm or replace your words. Then paste the draft into the detector above and look at contraction rate, sentence-length variance and vocabulary spread. If they have collapsed, run Standard mode at Light strength with a custom style profile built from 300 words of your own unedited writing. The engine restores the variance and contraction pattern you naturally use. Check again and read it aloud. Our own grammar checker at /grammar-checker fixes errors and explains each one without proposing rewrites, which avoids the problem at the source.
What Humanize 360 does differently
Our engine is not a language model, so nothing it produces has a model's statistical fingerprint. It measures your text and adjusts it toward how people write, keeps protected words untouched, and shows every change side by side. Your text is never sent to Grammarly, OpenAI or any other company, and anonymous runs are discarded when the result is sent. We cannot promise a detector result. We can make the writing sound like you.
Common questions
Why does Grammarly flag text I typed myself?
Usually because model-based suggestions were accepted throughout, which evens out sentence length and removes contractions and unexpected words. Our breakdown shows which of those signals moved.
Is the Humanize 360 grammar checker a rewriter?
No. It corrects errors and explains each correction, with a UK and US toggle. It does not propose full-sentence rewrites, so it does not push your writing toward a machine shape.
Can I use Grammarly and Humanize 360 together?
Yes. Use Grammarly for error correction, decline the rewrites, then check the draft here. If variance and contractions have collapsed, run Light strength with your own style profile.
Does Humanize 360 promise a result on Grammarly's detector?
No. No tool can, and detectors disagree with each other. We remove the tells all of them react to and show you the evidence.