QuillBot AI Detector: Review & Free Check
Paste any text below for a free AI score, no account needed. This is Humanit's checker, not QuillBot's. Under it: what QuillBot's free and Premium detectors give you, how it separates AI-generated from AI-refined text, and how far to trust it.
QuillBot's AI detector is free for up to 1,200 words per scan and six scans a day, with unlimited length and scans on Premium. It separates text generated with AI from text refined with AI, recommends at least 80 words for accuracy, and QuillBot itself says scores are signals, not verdicts.
Works with every major AI model
How it works
- 1Paste your text. Drop in the writing you want to check against QuillBot-style detection.
- 2Run the free detector. Humanit returns a 0–100 AI-likelihood score, a verdict, and the signals behind it.
- 3See what reads as AI. The subscores show which patterns — predictable phrasing, uniform rhythm, stock vocabulary — are pulling the score up.
- 4Fix it if needed. If it reads as AI, send it to the humanizer to rewrite those signals, then re-check.
Free vs Premium: what QuillBot's detector gives you
QuillBot's free AI detector checks up to 1,200 words per scan, up to six scans a day, and includes one explainer card showing why a passage was flagged. Premium removes the word limit, allows unlimited scans, unlocks explainers across the full text, and lets you download and share the report. QuillBot recommends at least 80 words per scan for accuracy, and says the detector is trained to recognise text from GPT-5, Gemini, Claude, Llama and other models.
AI-generated vs AI-refined
QuillBot's pitch is that most detectors cannot tell text generated with AI from text a person wrote and then refined with AI assistance — which is exactly what paraphrasers and grammar checkers, including QuillBot's own, produce. Its detector tries to separate the two. That is a sensible goal, and it gives you a more useful reading of a mixed draft than a single percentage. It is still an inference from the style of the words, so a human draft that was edited heavily can land in the refined bucket.
Does QuillBot's own paraphraser get flagged?
This is the question behind a lot of searches, and the honest answer is: it can. A paraphraser swaps words and reorders clauses, but the underlying rhythm and predictability that detectors measure often survive, so paraphrased AI text is frequently still flagged — by QuillBot's detector and by others. QuillBot also sells a separate AI humanizer for that reason. If Turnitin is the tool that matters for you, can Turnitin detect QuillBot? covers what it sees, and the QuillBot alternative page compares the rewriting side.
How accurate is QuillBot's AI detector?
QuillBot cites independent evaluations on RAID, an academic detection benchmark, for a very high detection rate. Benchmark results describe the benchmark's texts, not yours. QuillBot's own page is admirably direct about the limits: scores are signals, not verdicts, and no academic or employment decision should be made on a detector score alone. Independent research on detectors as a class agrees — a 2023 peer-reviewed study in Patterns found more than 61% of genuine TOEFL essays by non-native English speakers misclassified as AI — so treat a QuillBot result as a prompt to look closer.
What to do if QuillBot flags your writing
Read the explainer on the flagged passage first; it usually points at even sentence rhythm, generic phrasing or stock transitions. Vary sentence length, replace general claims with specific ones and cut filler such as "moreover" and "in conclusion". Keep your drafts and version history as evidence of how you wrote the piece. If you used AI and it is allowed, QuillBot itself advises disclosing that rather than revising only to change a score — sound advice for any detector.
A second check, with the reasoning shown
Humanit's detector above is free with no account for up to 300 words per check — a smaller free limit than QuillBot's, to be clear. It returns a 0–100 score split into sub-signals such as perplexity, burstiness, AI vocabulary and structure, lists the exact phrases pulling the score up, and has a humanizer on the same page. When two detectors disagree about a passage, that passage is in the grey zone, and it is worth rewriting in your own words.
Who it's for
| Feature | QuillBot AI detector | Humanit detector |
|---|---|---|
| Free limit | 1,200 words per scan, 6 scans a day | No account: 300 words per check, no daily cap |
| Longer checks | Premium: no word limit, unlimited scans | Free account: 1,500 words per check; plans up to 6,000 |
| AI-generated vs AI-refined | Separates the two | No, one 0–100 score with sub-signals |
| Explains why | 1 explainer card free, full on Premium | Sub-signals plus flagged phrases, free |
| Minimum length | 80 words recommended | Works on shorter text, less reliably |
| Rewrite flagged text in place | Separate humanizer and paraphraser | Yes, humanizer on the same page |
Frequently asked questions
Is this the official QuillBot AI detector?
No. This is Humanit's free detector, useful as a second opinion. QuillBot's own detector is at quillbot.com.
Is QuillBot's AI detector free?
Yes, for up to 1,200 words per scan and up to six scans a day. Premium removes the word limit, allows unlimited scans and unlocks full explainers.
Is QuillBot's AI detector accurate?
QuillBot cites independent RAID benchmark evaluations for a very high detection rate, and also says scores are signals, not verdicts. Independent research on detectors in general finds real false positives, so use its result to look closer, not to conclude.
Can QuillBot detect its own paraphrased text?
Often, yes. Paraphrasing changes words but tends to keep the rhythm and predictability detectors score, and QuillBot's detector is built to spot AI-refined text specifically.
What does AI-refined mean in QuillBot's detector?
It means the text looks like human writing that was polished with AI assistance, such as a paraphraser or grammar tool, rather than generated from scratch. It is an estimate from the style of the text.
How many words does QuillBot AI detector need?
QuillBot recommends at least 80 words per scan for accuracy. Very short passages give every detector too little signal.
Will my text be used to train AI?
No. Your text is sent to the model only to produce your result and is never used to train any AI. No content is stored beyond the request.
Does it keep my original meaning?
Yes. Humanit preserves your facts, numbers, names, and citations while changing the phrasing and structure. It never invents new claims.