Turnitin Similarity FAQs
Here are some of the most common questions users ask about Turnitin Similarity reports:
1. What is Turnitin Similarity?
Turnitin Similarity is a text-matching system designed to help identify how much of a submitted document matches existing content from a wide range of sources. These sources include academic journals, published books, student papers, conference proceedings, and publicly available web pages. The goal of Turnitin Similarity is not to accuse users of plagiarism, but to provide a detailed comparison report that highlights overlapping or matching text.
The similarity report allows educators, institutions, and writers to review matched sections and determine whether the similarities are acceptable (such as properly cited quotations or references) or problematic (such as uncited copying or excessive reliance on source material). Turnitin does not make judgments; it simply presents data that must be interpreted responsibly.
2. How does Turnitin calculate the similarity percentage?
Turnitin calculates the similarity percentage by comparing the submitted document against its databases and identifying text matches. The percentage represents the portion of the document that matches existing sources, not the portion that is plagiarized.
For example, if a paper contains references, direct quotes, commonly used phrases, or technical terminology, these may all contribute to the similarity score. Turnitin groups matching text into “similarity matches,” which are then highlighted in the report along with their source links. The final similarity percentage is the total matched content divided by the total word count of the document.
3. Is a high similarity score always bad?
No, a high similarity score is not automatically a sign of plagiarism. In many cases, high similarity results from correctly cited quotations, extensive reference lists, or standardized language used in academic or technical writing.
For instance, literature reviews, legal documents, or methodology sections often contain unavoidable similarities. What matters most is how the matched content is used. Instructors and reviewers are encouraged to examine the report carefully rather than relying solely on the percentage. Context, citation accuracy, and academic intent are critical when interpreting results. Read more
4. What similarity percentage is generally acceptable?
There is no universal “safe” similarity percentage, as acceptable thresholds vary by institution, discipline, and assignment type. However, many universities consider similarity scores below 15–20% acceptable when references and quotations are excluded.
Some institutions set stricter limits, especially for original research or reflective writing, while others allow higher percentages for review-based or technical papers. Always follow your institution’s official guidelines. Using services like PlagAiReport to check your work early helps ensure compliance before final submission. Read more
5. Does Turnitin detect paraphrasing?
Yes, Turnitin can detect poorly paraphrased content. If a sentence retains the original structure, phrasing, or sequence of ideas too closely, Turnitin may still identify it as a match.
Effective paraphrasing involves more than changing a few words. It requires rethinking the idea, restructuring sentences, and expressing the information in a genuinely original way, while still crediting the source. Turnitin is particularly effective at detecting “patchwriting,” where small edits are made to copied text without true originality.
6. Can Turnitin detect plagiarism from websites?
Yes. Turnitin compares submissions against billions of web pages, including blogs, academic websites, news articles, and online publications. It continuously updates its web database to capture new and modified content.
This means that copying content from the internet, even from less-known websites, is likely to be detected. Simply rewording web content without proper citation can still result in significant similarity matches.
7. Does Turnitin include student papers in its database?
Yes. By default, many Turnitin submissions are stored in the student paper repository. This allows Turnitin to compare future submissions against previously submitted student work.
However, this can lead to self-plagiarism issues if you later submit a revised or related version of the same paper. To prevent this, services like PlagAiReport offer a No Repository option, allowing you to check your work without adding it to Turnitin’s database. Read more
8. What is self-plagiarism in Turnitin?
lf-plagiarism occurs when an author reuses their own previously submitted or published work without proper acknowledgment or permission. Turnitin may flag this content if the earlier work exists in its database.
This commonly affects students submitting drafts, revised assignments, or reused sections from earlier coursework. Even though the work is your own, institutions often require original submissions for each assignment. Using No Repository checks can help avoid unintended self-plagiarism flags.
9. Can I exclude references from the similarity report?
Yes. Turnitin allows reviewers to exclude bibliographies, reference lists, quoted material, and small matches (such as short phrases) from the similarity calculation.
Excluding these elements helps provide a clearer picture of meaningful matches and reduces inflated similarity scores. While exclusions do not change the original submission, they significantly improve report interpretation and fairness.
10. Is Turnitin Similarity 100% accurate?
Turnitin is highly reliable, but it is not infallible. It is a matching tool, not a plagiarism judge. Similarity reports must always be reviewed by a human to determine intent, context, and academic integrity.
False assumptions can occur if similarity percentages are taken at face value without examining the highlighted content. Proper understanding, ethical writing practices, and informed interpretation are essential for accurate conclusions.