Turnitin Similarity Report: What Your Score Means
Reviewed by Prof. Dr. Alexander Holtermann · Updated 16 October 2026 · 6 min read
A Turnitin similarity score shows how much of your text matches other sources. It is not a plagiarism verdict: a person judges each match in context.
Key takeaways
- Turnitin, iThenticate, SafeAssign and similar services compare your text with web pages, publications and previously submitted student papers and highlight matching passages.
- The similarity percentage is the share of your text that matches other sources. Correctly quoted and referenced passages, the reference list and common phrases also count unless filtered.
- There is no universal “safe” percentage. A 25 % score can be harmless and a 6 % score can contain a serious problem; your instructor reviews the individual matches.
- AI writing indicators are separate from the similarity score and can produce false positives; universities are advised not to base decisions on them alone.
- The best protection is clean source work: quotation marks plus citation for wording, real paraphrasing with citation for ideas, and notes that separate your words from sources.
How universities check for plagiarism
Most universities in the US, UK, Australia and elsewhere use text-matching software when you submit coursework through the learning management system (for example Canvas, Moodle or Blackboard). The best known is Turnitin; its sister product iThenticate is used for theses, journal articles and by publishers (for example through Crossref’s Similarity Check). Other systems include SafeAssign (integrated into Blackboard) and various other services; Ouriginal (formerly Urkund) is now part of Turnitin.
These systems do not “detect plagiarism”. They detect similarity: passages in your text that match text in their databases. Whether a match is plagiarism is a judgement made by your instructor or an academic integrity panel, taking into account quotation marks, citations and context (Weber-Wulff, 2014).
What is in a similarity report?
A similarity report usually shows:
- Overall similarity score: the percentage of your text that matches sources.
- Highlighted passages: matching text in your document, colour-coded by source.
- Source list: each matching source with its share (for example 4 % from a journal article, 2 % from a website, 1 % from another student paper).
- Filters: instructors can exclude quoted material, the bibliography and very short matches, which often lowers the score considerably.
- Source types: internet pages, published works (journals, books) and a repository of student submissions from many institutions.
Why the percentage alone proves nothing
There is no official threshold. Some instructors look more closely above 15 % or 20 %, but that is a local rule of thumb, not a standard. The percentage depends on:
- Assignment type: a literature review with many quotations or a lab report with standard method descriptions naturally scores higher than a reflective essay. - Filter settings: whether quotes, bibliography and small matches are excluded. - Length: in a short text, one quoted sentence is already several percent. - Repository matches: if you submitted a draft earlier, or a classmate shared your file, your own text may match.
Conversely, a low score does not mean a text is original: unattributed paraphrasing of ideas, translated text, or content from sources not in the database can stay undetected. That is why instructors read the report, not just the number.
| Match type | Usually a problem? | What to do |
|---|---|---|
| Quoted text with quotation marks and citation | No | Check that quotation marks and page numbers are correct |
| Reference list entries | No | Nothing; often filtered out |
| Common phrases, technical terms, names of scales | No | Nothing |
| Close paraphrase with citation | Possibly | Rewrite more in your own words and structure |
| Copied text without quotation marks, with citation | Yes (patchwriting) | Add quotation marks or paraphrase properly |
| Copied text without citation | Yes | Quote or paraphrase and cite |
| Your own earlier assignment | Possibly (self-plagiarism) | Ask permission to reuse and cite your earlier work |
AI writing detection
Turnitin and other vendors also offer AI writing indicators that estimate how much of a text may have been generated by AI. This is a separate feature from the similarity score and is visible to instructors depending on the institution’s settings. Such indicators can produce false positives, for example for very formulaic writing or texts by non-native speakers, and vendors themselves say they should not be the sole basis for an academic misconduct decision.
If your university permits certain AI uses, document them (for example in an AI use statement or log). Professor Digital records every AI-assisted step in your AI log, from which you can create a declaration in your university’s format. If you are questioned, version history, notes and drafts are the best evidence of your own work.
Can you check your own work before submission?
Some universities let you submit a draft to Turnitin before the final deadline and see your report. Ask your instructor or check the course page; this is the safest self-check, because it uses the same system and settings.
Be careful with free online plagiarism checkers: some store or reuse uploaded texts, which can later lead to matches with your own work, and many do not search the same databases. Never upload a thesis containing confidential or participant data to an unknown service.
A reliable manual self-check takes an hour and catches most problems:
- Search your draft for every passage you copied into your notes and make sure each has quotation marks and a citation, or is paraphrased.
- Compare paraphrases side by side with the original: different words AND different sentence structure, plus citation.
- Check that every in-text citation appears in the reference list and vice versa.
- Mark reused passages from your own earlier assignments and ask your instructor whether reuse is allowed.
What happens if your score is high?
A high score does not automatically lead to an investigation. Your instructor reviews the matches. If there are concerns, the next step depends on your university’s academic integrity policy: an informal conversation, a resubmission, a mark reduction, or a formal process in serious cases. Stay calm, look at the report with your instructor, explain how you worked and bring your notes and drafts. Being able to show your process helps more than anything else.
Turnitin, iThenticate and others at a glance
A brief, general overview of common systems; availability depends on your institution.
| System | Typical use | Who sees the report |
|---|---|---|
| Turnitin (Feedback Studio, Similarity) | Coursework in learning management systems | Instructor; students if enabled |
| iThenticate | Theses, dissertations, journal manuscripts, publishers | Researchers, graduate schools, editors |
| SafeAssign | Coursework in Blackboard | Instructor; students if enabled |
| Other text-matching services | Varies by country and institution | Varies |
Frequently asked questions
What is a good Turnitin similarity score?
There is no official good or bad score. Many essays fall below 15–20 %, but what matters is what the matches are. Quoted and referenced text and the reference list are not plagiarism.
Does Turnitin detect plagiarism?
No, it detects text similarity. Your instructor decides whether a match is plagiarism by checking quotation marks, citations and context.
Does Turnitin count quotes and references?
By default they may count, but instructors can exclude quoted material and the bibliography. That is why a correctly referenced paper can still show a noticeable score.
Can Turnitin detect ChatGPT?
Turnitin offers a separate AI writing indicator. It is an estimate, can produce false positives and should not be the only basis for a decision. Follow your university’s AI policy and document permitted AI use.
Why does Turnitin match my own work?
Your earlier submission may be stored in the student paper repository, or a draft was submitted before. Tell your instructor; reusing your own work may require permission and citation.
Can I check my paper in Turnitin before submitting?
Only if your university allows draft submissions. Ask your instructor. Be careful with free online checkers that may store your text.
Sources and further reading
- Weber-Wulff, D. (2014). False Feathers: A Perspective on Academic Plagiarism. Springer.
- American Psychological Association. (2020). Publication Manual of the American Psychological Association (7th ed.).
- Turnitin and iThenticate guidance on interpreting similarity reports (consulted 2026).
Your university’s examination regulations and style guide always take precedence.
Related articles
- Avoiding plagiarismCite every idea, quote, and data point you take from others, paraphrase properly, never reuse graded work without permission, and track your sources.
- Quote, paraphrase, summarizeQuote when exact wording matters, paraphrase to restate one idea in your own words, summarize to condense main points. All three need a citation.
- AI in academic writingAI rules vary by university and course. Check the policy, use AI for support rather than ghostwriting, verify every claim, and disclose your use as required.
- Declaration of originalityA declaration of originality is a signed statement that your work is your own, sources are cited, and it was not submitted elsewhere.
- Reference listA reference list contains every source cited in your text; a bibliography may include works you consulted. APA says “References”, MLA “Works Cited”.
