Direct answer
The short answer is: it depends on which Grammarly features you use. Standard grammar, spelling, and punctuation checks through Grammarly do not typically show up on Turnitin's AI detection report. However, Grammarly's generative AI features—such as GrammarlyGO, AI-powered full-sentence rewrites, and "Rewrite with AI" suggestions—can produce text patterns that Turnitin's AI detector recognizes as AI-generated. Turnitin's FAQ explicitly addresses this by distinguishing between assistive tools (non-generative editing) and generative tools that create new content from scratch [1].
Does Turnitin Detect Grammarly as AI Writing?
Turnitin's AI writing detection model analyzes text at the sentence level, examining word probability patterns to determine whether content was written by a human or generated by an AI tool [2]. Human writing tends to be inconsistent and idiosyncratic, resulting in low-probability word sequences, whereas AI-generated text follows more predictable, high-probability patterns.
Grammarly offers two broad categories of features. The first category includes traditional proofreading tools—spelling corrections, punctuation fixes, conciseness suggestions, and basic grammar adjustments. These features do not generate new text; they adjust existing words or punctuation. Turnitin has confirmed that standard grammar-checking tools operating this way are not flagged as AI writing [1].
The second category includes Grammarly's generative AI features, most notably GrammarlyGO (now rebranded as "Grammarly" with generative capabilities), which can draft entire paragraphs, rewrite sentences with a different tone, or generate new content based on brief prompts. When these features produce novel text, Turnitin's model may detect the AI-like word probability patterns and flag those segments in the AI Writing Report [2]. The key distinction is whether the tool is editing your text or generating entirely new sentences on your behalf.
What Percentage of AI Score Does Grammarly Cause on Turnitin?
The AI score Grammarly might trigger on Turnitin varies significantly based on how extensively you use Grammarly's generative features. If you only use Grammarly for minor grammar fixes and punctuation adjustments, the AI score is likely to remain at 0%, as Turnitin's model treats this as human writing with edits [1]. Turnitin's report displays scores below 20% as an asterisk (*%) to account for potential false positives in this range [2].
If you use GrammarlyGO or AI-powered rewriting on entire paragraphs, the affected sentences may be highlighted in the AI Writing Report. However, the overall percentage depends on what proportion of your document contains AI-generated text. A document where only 5–10% of sentences were rewritten by Grammarly's AI may still show a relatively low overall percentage, whereas a document substantially composed using Grammarly's generative features could show a significantly higher score [2].
Turnitin's detection model takes into account that AI paraphrasing tools—which include Grammarly's rewriting features—may produce text that differs from direct AI generation. The AI Writing Report now includes a separate detection category for "AI-generated text that was AI-paraphrased," highlighted in purple, distinct from the cyan highlights used for directly AI-generated text [2]. This means Turnitin can identify text that was originally AI-generated and then reworded using Grammarly's paraphrasing capabilities.
How Can You Check If Grammarly-Edited Text Flags Turnitin Before Submitting?
Before submitting a paper that has been edited with Grammarly to your institution's learning management system, you can preview your Turnitin AI score using a Turnitin checking service. This allows you to see exactly which sections of your document Turnitin's AI detector identifies as potentially AI-generated before your instructor ever sees the report [4].
The AI Writing Report provides a detailed breakdown showing the overall percentage detected as AI, along with a submission breakdown that separates "AI-generated only" text from "AI-generated text that was AI-paraphrased" [2]. By reviewing this report, you can identify whether Grammarly's specific suggestions or rewrites are contributing to your AI score and make informed decisions about which edits to keep or revise.
When you upload your document to be checked, ensure it meets Turnitin's file requirements—at least 300 words of prose text in a long-form writing format, in a supported file type such as.docx,.pdf, or.txt [2]. The report will highlight specific sentences that triggered detection, giving you actionable feedback on which Grammarly-edited passages may need further revision to read more naturally as human writing [1].
If you've used Grammarly to polish your essay and want to see exactly how Turnitin will score your work before you submit it officially, you can run a real Turnitin AI and similarity check to preview your report with complete confidence.
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FAQ
Does Grammarly Premium trigger Turnitin AI detection?
Grammarly Premium includes the same standard grammar, clarity, and tone suggestions as the free version, plus advanced features like full-sentence rewrites and formality adjustments. The basic suggestions remain non-generative and generally safe. However, Premium's generative AI rewrites may be detected by Turnitin, just as GrammarlyGO would be [1].
Can Turnitin tell if I used Grammarly specifically?
Turnitin does not identify the specific tool used—it only determines whether text appears to be AI-generated based on statistical patterns. The AI Writing Report does not display "Grammarly detected"; it simply highlights sentences that the model predicts were written by an AI tool [2].
Will Grammarly show up on Turnitin's similarity check?
Grammarly's output itself is not stored in a public database, so Grammarly-edited text will not match any source in Turnitin's similarity database. The AI detection and similarity score are separate metrics—Grammarly affects the AI detection dimension, not the plagiarism/similarity dimension [1].
What if I only use Grammarly for spelling and punctuation?
Using Grammarly exclusively for non-generative corrections—spelling fixes, punctuation adjustments, and basic grammar corrections—is unlikely to trigger Turnitin's AI detection. These edits do not produce new text and therefore do not exhibit the word probability patterns associated with AI generation [1].
How can I make Grammarly-edited text less detectable?
Focus on using Grammarly's non-generative suggestions (word choice, punctuation, clarity) rather than AI-powered rewrites or full-sentence generation. If you do use AI rewrites, review each suggestion and manually adjust it in your own voice before including it in your document. You can also run a Turnitin check first to identify flagged sections and revise them accordingly [2].