Direct answer
Direct Answer - Yes, Turnitin checks for plagiarism and AI writing on every submission. Its Similarity feature compares your document against a vast database of student papers, premium publications, and more than 20 years of internet content, then returns a similarity score showing what percentage of your text matches other sources [1]. On top of that, a separate AI writing report estimates how much of your document may have been generated or paraphrased by AI tools [1]. Importantly, Turnitin flags matching text and probable AI writing, but it does not determine that plagiarism occurred — your instructor reviews the data and makes that judgment [1].
How Does Turnitin Detect Plagiarism In A Submitted Paper?
Turnitin's plagiarism check is powered by the Similarity Report, which runs automatically whenever a paper is uploaded. The service scans each submission against student papers already in its repository, current and archived web pages, and premium subscription articles across 170 languages, then assigns a similarity score equal to the percentage of matching or similar text uncovered [1]. Color-coded highlights and side-by-side source comparisons let your instructor see exactly where every match comes from [1].
The same submission is also processed by Turnitin's AI writing detection model. When a paper enters Turnitin, sentences are extracted and segmented into overlapping sections; each segment is classified by the model and given a probability value between 0 and 1 indicating whether it is likely human or AI-generated [2]. These sentence-level scores are then pooled and aggregated into the overall AI writing percentage that appears as an indicator on the report [2].
That indicator is not visible to students — only instructors and administrators can see it, and it is delivered inside the Similarity Report rather than the LMS interface [2]. Turnitin is explicit that its technology does not make a determination of misconduct; it provides data so educators can make informed decisions based on their academic and institutional policies [2].
What Is The Difference Between Turnitin's Similarity Score And AI Score?
The similarity score measures copied or closely matched text. It answers "how much of this paper appears elsewhere?" by comparing your words against Turnitin's database of web pages, publications, and prior student submissions [1]. The AI score answers a completely different question: "how likely is it that this text was written by an AI tool such as ChatGPT?" Turnitin states plainly that the AI writing percentage is different from and independent of the similarity score [3].
The two scores also display very differently. The AI Writing Report shows an overall percentage of qualifying prose that the model predicts was generated by an LLM or further modified by an AI paraphraser or bypasser tool, with likely AI text highlighted in blue in the submission breakdown [3]. Those AI highlights are not visible inside the Similarity Report itself, which instead focuses on color-coded matches against external sources [3].
Reading the numbers requires care. AI percentages between 0 and 19 are displayed as an asterisk (*%) rather than a number, because Turnitin found a higher incidence of false positives in that range and wants to prevent misinterpretation [3]. Only scores between 20 and 100 appear as a numeric percentage, and Turnitin recommends the AI indicator never be used as the sole basis for action against a student [3].
How Can I Check My Paper With Turnitin Before Submitting?
Here is the catch most students miss: you cannot simply run your own paper through Turnitin whenever you want. As a student, you cannot self-check a paper within Turnitin without uploading it to an official assignment created by your instructor, unless your institution has enabled Turnitin Draft Coach [4]. If Draft Coach is not available, your only in-Turnitin option is submitting to an assignment that allows resubmissions — and even then, only the first three attempts generate a report immediately, while later resubmissions require a 24-hour wait [4].
If your instructor has disabled resubmissions, your first attempt is final, and you will not see a report before that upload counts toward your grade [4]. That means many students only discover their similarity and AI scores after the assignment is already submitted — often too late to fix a citation error or rewrite a flagged paragraph.
Because institutional access is so restricted, students who want to know what Turnitin will flag before the deadline commonly turn to independent checking services that deliver the same official Turnitin reports instructors see in their systems — similarity score, AI percentage, flags, and match highlights — while there is still time to revise. A pre-submission check lets you fix paraphrasing, citations, and flagged AI text before your instructor ever sees it.
You now know exactly what Turnitin checks: text similarity against millions of sources plus an independent AI writing estimate — and you know Turnitin itself does not let you preview these reports before the final upload. That is precisely what turnitin0 solves: upload your draft and receive the real Turnitin AI and similarity reports your professors see, before you submit anything. Here is what an actual report from turnitin0 looks like:
※ Turnitin0.com - Actual Turnitin AI Report Cover, Score, Flag And Similarity Summary
FAQ
1. Does Turnitin check for both plagiarism and AI writing?
Yes. Every submission is processed for text similarity against Turnitin's database, and — when enabled by the institution — for AI-generated writing. The two checks run side by side in the same submission workflow [1][2].
2. Is a high similarity score the same as plagiarism?
No. The similarity score is only the percentage of matching or similar text found, and Turnitin states it does not determine whether plagiarism has occurred. Instructors review the matches and make that judgment [1].
3. Why does my Turnitin report show *% instead of an AI number?
AI scores below 20% are displayed as an asterisk because Turnitin found a higher incidence of false positives in that range and chooses not to surface a potentially misleading number [3].
4. Can I see my own Turnitin report before submitting?
Only if your institution enables Turnitin Draft Coach or your instructor's assignment allows resubmissions; otherwise, your first submission is also your final one [4].
5. Do the similarity score and the AI score influence each other?
No. Turnitin describes the AI writing percentage as different from and independent of the similarity score, so copied text and AI-generated prose are measured separately [3][2].