Direct answer
QuillBot does not "change" a plagiarism score in the way the phrase suggests: its Paraphraser rewrites wording, and its Plagiarism Checker reports a similarity percentage against its own source index, not against your institution's Turnitin database. Paraphrasing can lower word-for-word overlap, but it cannot remove a source from existence, and Turnitin's similarity report will still match paraphrased passages that keep the same structure and citations — and Turnitin's AI detector may flag heavily rewritten text as AI-assisted [1]. The only reliable way to know what your instructor will see is to run your own draft through a real Turnitin similarity and AI report before you submit.
Does QuillBot actually change your plagiarism score?
QuillBot's Plagiarism Checker works by comparing your text against a large index of web pages and academic sources and returning a similarity percentage alongside highlighted matched passages [1]. That percentage is a measure of textual overlap, not a judgement about intent, so a low number is not a guarantee of originality and a high number is not automatically misconduct — matched passages have to be read in context, including whether they are properly quoted and cited [1]. When students say a "plagiarism changer" lowered their score, what usually changed is the wording of matched sentences, not the underlying borrowing of ideas, structure, or evidence.
The critical limitation is the comparison set. QuillBot's checker searches its own index, which is not the same corpus your university uses; Turnitin's similarity report compares your draft against its own repository of web content, publications, and — depending on your institution's settings — previously submitted student papers [1]. A score from one tool therefore does not transfer to the other, and a clean result from a third-party checker is not evidence that your Turnitin report will be clean [1]. Treat any similarity percentage as tool-specific rather than as an absolute property of your essay.
There is also a second-order effect that students rarely anticipate. Turnitin's AI writing detection analyses patterns across whole passages, so text that has been run through a paraphraser to disguise its origin can still register as AI-generated, and can even score higher than the original draft because the rewriting introduces the flattened, uniform cadence that detectors associate with machine text [1]. In other words, "changing" the plagiarism signal can create an AI signal in its place.
Why does paraphrased text still get flagged as plagiarism or AI?
Paraphrasing changes surface wording, but similarity detection is not limited to exact string matching. Turnitin's report highlights passages that remain close to a source in vocabulary, sentence order, and phrasing even after synonym substitution, which is why a rewritten paragraph can still show up as a match [1]. If your paraphrase follows the original sentence-by-sentence — the classic "swap the words, keep the skeleton" approach — the overlap fingerprint often survives, and the report will show it.
The bigger risk is the AI side of the report. Turnitin's AI detector evaluates the statistical regularity of your prose, and paraphraser output tends to be regular: even sentence lengths, predictable transitions, and low burstiness. That is precisely the profile the detector is trained to notice, so a student who paraphrases an AI draft to beat the similarity checker may simply move the flag from the similarity column to the AI column [1]. Detectors also work at the passage level, so a single rewritten section can be flagged while the rest of the essay reads as human.
Finally, paraphrase does not address the parts of academic writing that similarity tools are designed to catch legitimately: direct quotations, standard method descriptions, common definitions, and reference lists. Those will match sources no matter how creatively the surrounding prose is rewritten, and they are expected to match [1]. A similarity score built largely from a bibliography and a methods section is normal; the number only becomes meaningful when you read which passages produced it.
How can you verify your similarity and AI score before you submit?
The only score that matters is the one produced by the system your institution actually uses, which in most universities is Turnitin. That means verifying with a genuine Turnitin similarity report and a genuine Turnitin AI writing report on your own draft, rather than extrapolating from a third-party checker's percentage [1]. Reading the actual highlighted matches tells you something a bare number cannot: whether the overlap sits in your citations and standard phrasing, or in the analytical passages where unattributed borrowing would be a real problem.
A pre-submission check also gives you the AI signal in the same format your instructor will see. Turnitin reports AI writing as a percentage of qualifying text, and it displays an asterisk instead of an exact figure when the detected amount falls below its confidence threshold — a low-confidence signal rather than a clean bill of health [1]. Knowing that distinction before you submit is far more useful than guessing from a paraphraser's output, because it tells you whether you have a drafting problem to fix or simply a citation style to tighten.
Use the report as a diagnostic, not a scoreboard. If the flagged passages are quotations and references, fix your quoting and citation practice; if they are your own analytical sentences, rewrite them from your own understanding of the source rather than through a paraphrasing tool [1]. Either way, the decision about what to change should be driven by the actual flagged text, which is why a real report beats a similarity percentage from a different index.
If you want to see the exact report your instructor will open — the similarity percentage, the highlighted matches, and the AI writing score on your own draft — turnitin0 runs your document through a genuine Turnitin check and returns both PDFs together, without adding your file to the student paper repository. Students use it to read the flagged passages and decide what genuinely needs rewriting before the deadline, rather than trusting a paraphraser's promise.
※ Turnitin0.com - Actual Turnitin AI Report Cover, Score, Flag And Similarity Summary
FAQ
Is QuillBot a plagiarism changer?
QuillBot is a paraphrasing and checking tool, not a way to erase plagiarism. Its Paraphraser rewrites wording and its Plagiarism Checker reports similarity against its own source index, so the number it returns is not the Turnitin score your university will see [1].
Can paraphrasing with QuillBot lower a Turnitin similarity score?
It can reduce word-for-word overlap on some passages, but Turnitin also matches paraphrased text that keeps a source's structure and phrasing, and quotations and references will always match [1]. A lower similarity figure is not the same as correctly attributed writing.
Will paraphrased text be flagged by Turnitin's AI detector?
It can be. Paraphraser output tends to be statistically regular, which is the pattern AI detection looks for, so rewriting an AI draft may shift the flag from similarity to AI rather than remove it [1].
Does QuillBot check against the same database as Turnitin?
No. QuillBot compares against its own index of web and academic sources, while Turnitin compares against its own repository, publications, and — where institutions enable it — previously submitted student papers [1].
What does an asterisk mean on a Turnitin AI report?
It means the detected AI text fell below Turnitin's confidence threshold, so the exact percentage is not displayed. It is a low-confidence signal, not proof that the writing is human [1].