Yes, Turnitin can flag text that has been run through QuillBot and similar paraphrasing tools. Turnitin added AI paraphrasing detection in December 2023, and its AI writing report now includes likely AI-generated text that was later changed by a paraphraser or bypasser tool in a single AI percentage.
Paraphrasing tools are popular because they promise to reword text quickly. The problem is that Turnitin now looks for exactly that pattern. This guide explains what Turnitin’s paraphrasing detection does, how it appears in a report, and when using these tools crosses into misconduct.
For how the AI detector works overall, read Turnitin AI detection explained.
Can Turnitin detect QuillBot?
Turnitin can detect text that is likely AI-generated and then reworded by an AI paraphraser such as QuillBot. Turnitin does not publish a list of the specific tools it detects, so it does not confirm QuillBot by name, and no independent tool-by-tool test has been published.
Two separate situations matter here. If you paste AI output into QuillBot to reword it, Turnitin is designed to catch that combination. If you paste your own writing into QuillBot, the output can still look machine-written because the tool rewrites sentence patterns. Either way, the reworded text may raise your AI score.
It is part of Turnitin’s AI writing model that looks for text likely written by AI and then altered by a paraphrasing tool or word spinner. From July 2024 this showed as a separate purple highlight. Since 4 August 2026 it has been merged into one AI category and one blue percentage.
| Date | Change (per Turnitin release notes) |
|---|---|
| December 2023 | AI paraphrasing detection added to the English model |
| July 2024 | Report separates AI-generated text from AI-generated text that was paraphrased (purple highlight) |
| 27 August 2025 | Detection extended to AI bypasser tools, often sold as humanisers |
| 4 August 2026 | Purple highlight removed; one AI category now covers generated, paraphrased and bypassed text |
The practical effect of the August 2026 change is that a tutor no longer sees a separate ‘paraphrased’ figure. They see one number. A report generated before that date may look different from one generated now for the same document. Paraphrasing and bypasser detection is English-only according to Turnitin’s documentation.
Does QuillBot change your similarity score?
It can lower exact word matches, so the similarity score may drop. That does not make the work original. Close paraphrasing without citation is still plagiarism, and the AI score may rise at the same time. You can end up trading a similarity problem for an AI writing problem.
The similarity score and AI score are independent measurements, so one going down tells you nothing about the other. If you want a lower similarity score, the honest route is better citation and genuine paraphrasing in your own words. See how to lower your Turnitin similarity score honestly.
Is using a paraphrasing tool academic misconduct?
It depends on your university’s rules and how you use the tool. Rewording someone else’s work without citation is plagiarism regardless of the tool. Many institutions also treat undisclosed AI rewriting as unauthorised AI use. Check your module’s AI policy before using any paraphraser.
Some universities allow AI tools for specific tasks if you disclose them, while others ban them for assessed work. When the policy is unclear, ask your tutor in writing and keep the reply.
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How can you use these tools within the rules?
Write your own draft first, then use tools only for the tasks your university allows, such as grammar checks. Disclose any permitted AI help. Cite every source you paraphrase. Keep your drafts and version history so you can show how the work developed.
- Learn to paraphrase by hand. Our guide to paraphrasing without plagiarising walks through it with examples.
- Avoid running AI text through a humaniser to hide it. Turnitin’s bypasser detection is built for that pattern.
- Check your final version before submission so there are no surprises. Upload your document for a similarity and AI report.
How does paraphrased AI text appear in the report?
Since August 2026 it has appeared as ordinary AI highlighting inside the single blue AI percentage. Your tutor sees highlighted sentences and one overall figure, not a separate paraphrasing number. Older reports from before that date may still show purple highlights for AI-paraphrased text.
Because only long-form prose counts, paraphrased bullet points or tables do not affect the AI score. That does not make them safe from the similarity check, which still compares every part of the document against Turnitin’s database.
If you are reviewing a report that mixes similarity matches and AI highlights, treat them as two separate tasks. Fix citations for the similarity matches. For AI highlights, compare the passage with your drafts and rewrite it in your own voice if it came from a tool.
What is the difference between paraphrasing tools and grammar checkers?
Grammar checkers correct spelling, punctuation and small errors while keeping your words. Paraphrasing tools rewrite whole sentences with AI. Turnitin says ordinary grammar corrections are generally not flagged, while AI rewriting, drafting and paraphrasing features are likely to be flagged as AI writing.
Tool feature Likely effect on Turnitin AI score Typical university view Spelling and grammar fixes Generally not flagged Usually allowed Tone or fluency rewrite May be flagged Check policy Full sentence paraphrasing Likely flagged Often restricted or must be disclosed Generating new text Likely flagged Banned unless explicitly allowed If you rely on a tool because English is not your first language, tell your tutor and ask what support is allowed. Many universities offer academic writing services that are safer than automated rewriting.
What should you do if a paraphrased passage is flagged?
Compare the flagged passage with your drafts. If you wrote it yourself, keep the drafts as evidence and explain your process. If it came from a paraphrasing tool, rewrite it in your own words from your notes, cite the source and disclose any tool use your policy requires.
Do not run the passage through another tool to make it look different. That repeats the same problem and can make the text harder to defend. Writing it again yourself is faster than it sounds, because you already know what the paragraph needs to say.
If you have time before the deadline, check the revised version so you know the passage no longer stands out. Our guide to checking your Turnitin score before submitting explains how.
Situation Best next step Your own writing flagged Keep drafts, explain process Tool-paraphrased text flagged Rewrite from notes, cite, disclose Unsure where text came from Rewrite the section from scratch
Frequently asked questions
Does QuillBot show up on Turnitin?
Text reworded by QuillBot can be flagged by Turnitin’s AI writing indicator, especially if the original text was AI-generated. Turnitin does not name the specific tools it detects.
Does QuillBot lower the Turnitin similarity score?
It may reduce exact matches, but uncited paraphrasing is still plagiarism, and the AI score may increase. The two scores are measured separately.
Is QuillBot’s grammar checker safe to use?
Turnitin says ordinary grammar and spelling corrections are generally not flagged. Rewriting and paraphrasing features are the ones likely to affect the AI score.
Does Turnitin still show purple highlights for paraphrased text?
No. Since 4 August 2026 Turnitin shows one AI category. Paraphrased and bypassed AI text is included in the single AI percentage.
Does paraphrasing detection work in every language?
No. Turnitin’s documentation says AI paraphrasing and bypasser detection is available for English only.
