Scribbr vs QuillBot AI Detector: AI detector comparison
A side by side look at pricing, methodology, language support and best-fit use case. Every claim on this page is linked to a source at the bottom.
Last updated . Reviewed by IsItAI Editorial.
At a glance
Scribbr
Netherlands, 2012 (AI detector 2023)Student-focused, integrated with Scribbr's plagiarism and citation tools.
- Pricing
- Pay-per-check from $9.95
- Free tier
- 1.2k words free
- API
- No
- Languages
- 4
QuillBot AI Detector
US, 2017 (AI detector 2023)Free detector from the company best known for paraphrasing tools.
- Pricing
- Free (Premium suite from $9.95/month)
- Free tier
- Free unlimited
- API
- No
- Languages
- 3
Side by side
| Feature | Scribbr | QuillBot AI Detector |
|---|---|---|
| Free tier | 1.2k words free | Free unlimited |
| Starting price | Pay-per-check from $9.95 | Free (Premium suite from $9.95/month) |
| Cost per 1k words | $0.30 | Free |
| API available | No | No |
| Languages supported | 4 | 3 |
| Founded | 2012 (AI detector 2023) | 2017 (AI detector 2023) |
| Country | Netherlands | US |
| Primary audience | Students and dissertation writers | Students and casual writers |
| Best for | Students already using Scribbr for proofreading or citations | Quick free checks alongside QuillBot's paraphraser |
| Known weakness | Pay-per-check pricing gets expensive fast and there is no API | Conflict of interest. The same company sells the paraphraser that defeats detectors |
How each tool works
Scribbr
Method: Detector white-labelled on top of Turnitin's underlying classifier per Scribbr's own published documentation.
Data handling: EU hosted. Submissions retained per Scribbr's published policy.
QuillBot AI Detector
Method: Free classifier within the QuillBot writing suite.
Data handling: Stores submissions for product improvement.
How accurate are AI detectors? What the research says
Two findings from independent academic research apply to almost every detector on this list, including Scribbr and QuillBot AI Detector.
1. False positives on non-native English writers. Liang et al. (Stanford, 2023) found that GPT detectors flagged over half of TOEFL essays written by non-native English speakers as AI-generated, while flagging almost none of the essays from US students. If your use case involves non-native English writers, never treat a detector verdict as proof on its own.
2. Paraphrasing reliably defeats classifiers. Sadasivan et al. (Maryland, 2023) showed that running AI output through a paraphraser drops detection performance close to chance. Both Scribbr and QuillBot AI Detector are vulnerable to this.
For a deeper breakdown of how accuracy claims hold up across 2026 testing, see our guide to how accurate AI detectors actually are in 2026.
Where Scribbr wins
- Runs on Turnitin's underlying classifier (white-labelled per Scribbr's own documentation), so it reflects the engine many universities use.
- Pay-per-check with no subscription, useful for a one-off dissertation check.
- EU hosted with a published retention policy.
Where QuillBot AI Detector wins
- Free and unlimited, versus Scribbr's pay-per-check pricing that adds up fast.
- Sits alongside QuillBot's paraphraser and grammar tools students already use.
- No per-check cost for repeated casual checks.
Which one should you pick, Scribbr or QuillBot AI Detector?
Pick Scribbr if you want a one-off check on the same Turnitin engine many universities run and do not mind pay-per-check pricing. Pick QuillBot if you want free, unlimited casual checks. Neither offers an API, and QuillBot's parent sells the paraphraser built to defeat detectors, a conflict of interest to keep in mind.
Frequently asked questions
Is Scribbr free?
1.2k words free
Is QuillBot AI Detector free?
Free unlimited
Can either tool be fooled by paraphrasing?
Yes. Sadasivan et al. (2023) demonstrated that paraphrasing reliably defeats most AI classifiers. Treat any detector verdict as a screening signal, not proof.
Are AI detectors fair to non-native English writers?
Independent research (Liang et al. 2023) found high false-positive rates for non-native English writing. Always combine a detector signal with other evidence, never use it as a sole basis for an academic or hiring decision.
Which one should I pick if I have to choose one, Scribbr or QuillBot AI Detector?
Pick Scribbr if you want a one-off check on the same Turnitin engine many universities run and do not mind pay-per-check pricing. Pick QuillBot if you want free, unlimited casual checks. Neither offers an API, and QuillBot's parent sells the paraphraser built to defeat detectors, a conflict of interest to keep in mind.
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Sources and further reading
- Scribbr AI detector
- Scribbr published comparison of AI detectors
- QuillBot AI detector
- Sadasivan et al. (2023): Can AI-generated text be reliably detected?
- Liang et al. (Stanford, 2023): GPT detectors are biased against non-native English writers