Direct answer
Turnitin checks for both. A single submission produces two independent layers of analysis: a similarity (plagiarism) report that compares your text against its databases of web pages, journals, and previously submitted papers, and an AI writing detection indicator that estimates how much of your prose was likely generated by a large language model [1]. The two reports are generated from the same upload but measure completely different things, so a clean similarity score tells you nothing about your AI score — and vice versa [1].
Does Turnitin Check for AI or Plagiarism — or Both?
Both, and they run as separate report layers on the same file. When an assignment is submitted, Turnitin generates a similarity report by matching your text against its content repository, and separately runs AI writing detection over the qualifying prose in the document [1]. Instructors see both outputs side by side in the assignment inbox, which is why one upload can trigger two very different conversations [1].
The critical thing to understand is that these are not two views of one score. The similarity report is built from source matching — it tells you where text overlaps with existing material [2]. The AI writing indicator is built from statistical patterns in the writing itself, and it does not need any matching source at all to flag a passage [3]. A student can therefore have 0% similarity and a high AI score, or 40% similarity and an asterisk for AI, and neither result contradicts the other [1][3].
This matters for how you prepare. If you only fix one dimension, you have only fixed half the risk. Rewriting a copied paragraph resolves a similarity match but does nothing to the AI indicator, and paraphrasing AI-generated prose by hand can leave the underlying statistical signature intact [3]. Treat the two checks as two separate audits of the same document [1].
How Is the Turnitin AI Writing Score Different From the Similarity Score?
The similarity score is a percentage of your document's text that matches sources in Turnitin's repository [2]. Turnitin highlights each matched string and links it to the source it came from, so the report is investigative rather than purely numerical — you can click through and see exactly what overlapped [2]. Importantly, a high similarity score is not automatically plagiarism: correctly quoted material, bibliography entries, and very short common phrases can all inflate the number, and instructors are expected to interpret the matches rather than read the percentage as a verdict [2].
The AI writing score works on an entirely different basis. It reports the percentage of your qualifying prose that the detector assesses as likely AI-generated, and it deliberately excludes sections that are not continuous prose — reference lists, quotes, and short strings are not evaluated [3]. Because it is a probabilistic model rather than a source comparison, it can flag original writing that happens to share stylistic features with model output, and it can miss AI text that has been heavily edited [3].
One practical detail students frequently misread: when the AI indicator falls below Turnitin's confidence threshold, the report displays an asterisk (*) instead of an exact percentage [3]. That asterisk is a low-confidence signal, not a zero and not a pass — it means the detector did not have enough signal to commit to a number [3]. The similarity score, by contrast, always displays as a figure because it is a direct measurement of matched text [2].
Can You See Your Turnitin AI and Similarity Results Before You Submit?
Usually not through your institution. In the standard Turnitin workflow, student visibility of the AI writing indicator is controlled by the instructor and the institution, and many courses never enable it for students at all [4]. Even where reports are visible, whether you can see them before a deadline depends on how the assignment and any draft-check folder were configured — settings the instructor chooses, not you [4].
That gap is the real problem. You are asked to submit a document that will be assessed on two independent dimensions, and in most institutional setups you get no preview of either one before the deadline [4]. Students who assume a low similarity score means they are safe are often surprised by the AI indicator, and students who rewrote their prose to sound less robotic may still be carrying similarity matches they never saw [1][4].
The workaround is to run the same two checks yourself before you upload. A pre-submission check that returns both a similarity report and an AI detection report — the same two documents your instructor sees — turns an invisible risk into a readable one [1]. You get the matched-source highlights and the AI percentage while you still have time to act on them, rather than after the grade is posted [2][4].
That is exactly what turnitin0 was built for: you upload your.docx,.pdf, or.txt file and receive two downloadable PDFs in one checkout — a Turnitin AI detection report and a similarity report, matching what professors see in their LMS. Turnitin0 is an independent service and is not affiliated with Turnitin, LLC, and your file is checked without being added to the student paper database. Most orders finish in 5–15 minutes, and 100,000+ reports have been delivered to 20,000+ students across the US, UK, Canada, Australia, New Zealand, and Ireland.
※ Turnitin0.com - Actual Turnitin AI Report Cover, Score, Flag And Similarity Summary
FAQ
Does Turnitin check for AI and plagiarism at the same time?
Yes. One submission generates a similarity report and an AI writing detection report as two separate layers of analysis on the same file [1]. They are produced from a single upload but measure different things and can be read independently.
Can Turnitin flag AI writing if there are no plagiarism matches?
Yes. The AI writing indicator does not require a matching source, because it evaluates statistical patterns in your prose rather than comparing it to a database [3]. A document with 0% similarity can still carry a high AI score.
What does an asterisk (*) mean on a Turnitin AI report?
It means the AI detection result fell below Turnitin's confidence threshold, so the report shows an asterisk instead of an exact percentage [3]. It is a low-confidence signal rather than a confirmed zero.
Is a high similarity score automatically plagiarism?
No. The similarity score is the percentage of text matching sources in the repository, and quoted material, bibliography entries, and short common phrases can raise it without any misconduct [2]. Instructors are meant to review the highlighted matches rather than the number alone.
Can I see my own Turnitin AI and similarity reports before submitting?
Institutional visibility is set by your instructor and institution, and many courses do not expose the AI indicator to students [4]. Running a pre-submission check that returns both reports is the reliable way to see them before your deadline.