Direct answer
Yes, Grammarly does detect AI-generated writing: its AI detector returns a percentage estimate of how much of a document its model considers likely machine-generated. That number is a probabilistic signal built for the writer, not an academic-integrity ruling, and it is produced by a different model from the one your university runs. A low Grammarly score therefore does not guarantee a clean Turnitin AI report, because the two tools segment text, weight evidence, and set thresholds differently [1].
Does Grammarly Detect AI-Generated Writing, And How Accurate Is It?
Grammarly ships an AI detector that scans an uploaded or pasted document and reports the share of text its model classifies as likely AI-generated, alongside a confidence signal for that estimate [1]. The verdict is document-level, so a single flagged paragraph can pull the headline number up even when the surrounding prose is entirely your own. Grammarly frames the output as a diagnostic for the author — something that tells you where your draft reads mechanically — rather than as evidence of misconduct [2].
Accuracy is best understood as conditional, not absolute. The detector is strongest on long, unedited, plainly machine-drafted passages, and weakest on short excerpts, heavily rewritten text, and technical writing where formulaic phrasing is normal [2]. Because the model is trained on specific corpora with specific thresholds, the same paragraph can land at 12% in one tool and 60% in another without either tool malfunctioning [1]. That is why Grammarly's own guidance treats its score as a prompt to revise, not as a certificate you can carry into a submission portal [2].
The practical consequence for students is that "Grammarly said it's fine" is not a defensible position if a different detector disagrees. Institutional decisions are made against the report the institution generates, and no third-party tool's output is binding on that report [2]. If your workflow leans on Grammarly as a first-pass screen, treat its result as one data point among several rather than the final word [1].
Why Can Text Pass Grammarly But Still Be Flagged By Turnitin's AI Detector?
The two systems answer slightly different questions. Turnitin's AI writing report breaks a document into qualifying segments and reports the proportion flagged as AI-generated, with an overall indicator layered on top [3]. Because the calculation runs at segment level, a small number of high-confidence flagged spans can push a document across a threshold that a whole-document average would never reach. Grammarly's headline percentage and Turnitin's segmented percentage are therefore not the same statistic, even when both are expressed as a percentage [1].
Training data and thresholds diverge as well. Turnitin states that its detector was trained on a large proprietary corpus and that its model is not directly comparable with third-party detectors, so a score from one cannot be mapped onto a score from the other [3]. Turnitin also documents that a *% display appears when the AI signal falls below its confidence threshold — a low-confidence indicator rather than an exact figure — which is a display convention no consumer tool replicates [4]. A student comparing screenshots across tools is often comparing two different measurement scales.
Editing behaviour explains most of the remaining gap. Light paraphrasing, synonym swaps, and reordered sentences preserve the statistical regularity that detectors key on, so a passage can read more naturally to a human while still scoring as machine-like to a classifier [3]. Conversely, genuine drafting followed by heavy AI polishing can leave flagged residue in exactly the transitions and summary sentences students tend to outsource. Turnitin's guidance is explicit that the report is an indicator to be interpreted in context, not a standalone finding [3].
How Can A Student Verify A Draft Against The Same Turnitin AI Report Their Instructor Sees?
The instructor's view of your work is the Turnitin report itself, generated from the file you submit. Turnitin's documentation confirms that the AI indicator is surfaced inside the report flow instructors already use, which means previewing that view requires running the same file through the same detector rather than approximating it with a different product [4]. Anything short of that leaves you comparing a proxy against the real instrument.
File-level fidelity matters more than most students expect. Reports are generated against the submitted file, so formatting, reference lists, headings, and the exact wording of the final version all belong in the preview — a check run on an earlier draft tells you about that draft, not the one you are about to upload [4]. Turnitin's FAQ also notes that the AI indicator is designed to be read alongside the similarity report, since the two signals are reviewed together in most institutional workflows [4].
This is the gap turnitin0.com was built to close. It runs your .docx, .pdf, or .txt through Turnitin and returns two downloadable PDFs in a single order — the AI detection report and the similarity/plagiarism report — matching what instructors see in their LMS. Checks are non-repository, so your file is not added to Turnitin's student paper database, English documents between 300 and 30,000 words are supported, and most orders finish in 5–15 minutes. Students pay per check with no subscription: $3.80 for a single check, or $2.75 per check in a 10-check pack.
If Grammarly has already told you your draft looks human, the remaining question is whether Turnitin's model agrees — and that is a question only the real report can answer. turnitin0.com gives you that report before your deadline does, so you can see the actual score, the flagged spans, and the similarity matches while there is still time to revise rather than after a mark has been decided.
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FAQ
Is Grammarly's AI detector the same as Turnitin's?
No. They are separate models trained on separate corpora with separate thresholds, and Turnitin states its detector is not directly comparable with third-party tools [3]. A percentage from one cannot be converted into the other.
Can a fully human-written essay be flagged as AI?
Yes, and Turnitin acknowledges that its indicator should be read in context rather than treated as a standalone finding [3]. Formulaic academic phrasing, heavy templating, and non-native English writing patterns are the most common sources of false positives.
What does a *% score mean in a Turnitin AI report?
It appears when the AI signal falls below Turnitin's confidence threshold, indicating a low-confidence detection rather than an exact percentage [4]. It is a display convention specific to Turnitin's report.
Does Grammarly's AI score protect me if my university uses Turnitin?
No. Institutional decisions rest on the report the institution generates from your submitted file, so a clean Grammarly result does not bind Turnitin [4]. Preview the real report if the distinction matters for your grade.
Which file should I check to preview my instructor's view?
The exact final file you intend to submit, including headings and references, because reports are generated against the submitted file [4]. Checking an earlier draft tells you only about that draft.