Turnitin and iThenticate Similarity Detection
Turnitin and iThenticate: Text-Matching Similarity Detection Tools for Plagiarism Screening · Also known as: text-matching software, plagiarism detection software, similarity detection, originality reports
Turnitin and iThenticate are commercial text-matching software tools used by educational institutions and academic journals to screen submissions for potential plagiarism. Turnitin is designed for student assignments; iThenticate is designed for researcher manuscripts. Both tools compare submitted text against billions of sources (web pages, academic databases, previously submitted documents) and generate a Similarity Index showing what percentage of the submission matches existing sources. These tools are screening instruments, not plagiarism detectors—they flag suspicious content for human review.
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When to use it
Turnitin and iThenticate are used by: (1) Educational institutions—most universities use Turnitin in learning management systems to screen student assignments; (2) Academic journals and publishers—editorial offices use iThenticate to screen submissions before peer review; (3) Research integrity offices—investigating potential plagiarism allegations; (4) Authors—who may submit their own work to these tools before submission to check for unintentional plagiarism; (5) Grant agencies—some require applicants to submit research integrity certifications using these tools.
Strengths & limitations
- Scalable screening—can process thousands of submissions rapidly and compare against billions of sources
- Comprehensive database—both tools access web content, published databases, and (for Turnitin) student submission repositories
- Visual reporting—color-coded matching and source-by-source breakdown helps reviewers quickly identify problem areas
- Detection of verbatim copying—excellent at identifying word-for-word copying, the most straightforward plagiarism form
- Documentation—creates auditable records of screening, useful for institutional accountability
- Cannot detect idea plagiarism—if text is completely rewritten but ideas are stolen, software may not flag it
- Cannot interpret context—high matching in a literature review section is normal; high matching in results is concerning, but software cannot distinguish
- Cannot assess citations—software flags matching text but cannot confirm that proper citations are present at that location
- High false-positive rate—many flagged items are legitimate (quotations, references, boilerplate text), requiring manual review to assess
- Database gaps—both tools have gaps in coverage; some sources are not indexed, so plagiarism may go undetected
- Language limitations—tools work best with English; detection quality decreases for other languages and for translated plagiarism
Frequently asked
What does a Similarity Index of 35% mean—does it mean I plagiarized 35%?
No. A 35% Similarity Index means that 35% of your text is similar to sources in the tool's database. This similarity may include quotations (which are legitimate if cited), references, boilerplate methods text, or actual plagiarism. The software cannot distinguish between these categories. You must review the detailed report to see what sources matched and whether those passages are properly quoted and cited. A 35% index could indicate serious plagiarism or could indicate legitimate academic writing with extensive quotations and citations.
Can I get a plagiarism penalty if Turnitin flags my work but I properly cited everything?
No. If all flagged matching text includes quotation marks and citations, you have not plagiarized. The software flags similarity; proper citations and quotation marks indicate that similarity is legitimate. However, this highlights why instructors must review reports carefully rather than penalizing based on Similarity Index alone. If an instructor penalizes you for high similarity despite proper citations, this is unjust. Show your instructor the detailed report and your citations, and ask for clarification.
Why does my paper show high similarity to my own previous published work?
This indicates self-plagiarism or text recycling. When you quote yourself without quotation marks or reuse paragraphs from previous work, the software flags it as similar to a prior publication. This is appropriate—most publishers require disclosure of prior publications and prohibit republication without permission. If you are building on previous work, disclose it in your cover letter and potentially in your methods section (e.g., 'Based on our prior work [citation], we...'). Rewrite substantially or obtain permission from the publisher.
If the plagiarism detection software doesn't flag my work, does that mean I haven't plagiarized?
No. Software detects textual similarity, not all forms of plagiarism. Idea plagiarism (taking ideas without attribution), some forms of paraphrasing plagiarism, and translation plagiarism may not be caught. Low similarity does not mean clean work. Conversely, high similarity does not mean plagiarized work. Software provides partial information. Human expertise is required for a complete plagiarism assessment.
Sources
- Turnitin. (2023). Turnitin similarity detection and plagiarism detection technology. Retrieved from https://www.turnitin.com/products/similarity link ↗
- Turnitin (iThenticate division). (2023). iThenticate: Originality checking for researchers. Retrieved from https://www.ithenticate.com link ↗
- Declerck, K., Decock, P., Macq, B., & Vandenbossche, J. (2021). Similarity index in plagiarism detection: A critical perspective. Research Integrity and Peer Review, 6, 1-8. link ↗
How to cite this page
ScholarGate. (2026, June 4). Turnitin and iThenticate: Text-Matching Similarity Detection Tools for Plagiarism Screening. ScholarGate. https://scholargate.app/en/research-ethics/turnitin-ithenticate
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
- Similarity vs Plagiarism: Understanding the DistinctionResearch Ethics↔ compare
- Verbatim PlagiarismResearch Ethics↔ compare