Self-plagiarism on Turnitin is one of the most common shocks for postgraduate students. You did not copy anyone else — yet the report shows near-total similarity. The match source is often your own earlier upload.
How Turnitin treats stored papers
When a submission is stored in a repository, later submissions can match that stored text. If draft 1 was indexed, draft 2 (even improved) may match draft 1 heavily.
Common causes in Sri Lanka
- Using free “Turnitin” sites that store files.
- Checking via a classmate’s student account with repository on.
- Uploading early chapters to LMS for feedback, then re-uploading the full thesis.
- Multiple supervisors requesting separate portal uploads.
How to prevent it
- Never use repository-on tools for unfinished drafts.
- Use No-Repository instructor checks for private pre-submission scans.
- Keep one official final submission path for your university.
- Document your revision history for viva or supervisor discussions if needed.
No-Repository mode is the practical fix for revision-heavy work like MPhil/PhD theses and final-year projects.
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Official Similarity + AI reports in No-Repository mode. Built for students and researchers in Sri Lanka.