IsItAI 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
IsItAI
UK, 2024UK-built AI detection that gives you a confidence score, not a verdict.
- Pricing
- From £4.99/month
- Free tier
- 5 scans/day free
- API
- Yes
- Languages
- 30
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 | IsItAI | QuillBot AI Detector |
|---|---|---|
| Free tier | 5 scans/day free | Free unlimited |
| Starting price | From £4.99/month | Free (Premium suite from $9.95/month) |
| Cost per 1k words | £0.05 (Pro plan equivalent) | Free |
| API available | Yes | No |
| Languages supported | 30 | 3 |
| Founded | 2024 | 2017 (AI detector 2023) |
| Country | UK | US |
| Primary audience | Educators, recruiters and content teams | Students and casual writers |
| Best for | Teachers, students and recruiters who want a clear confidence score and source-passage highlighting | Quick free checks alongside QuillBot's paraphraser |
| Known weakness | Smaller brand than US incumbents | Conflict of interest. The same company sells the paraphraser that defeats detectors |
How each tool works
IsItAI
Method: Multi-model ensemble. Combines several open detectors and weights agreement. Returns a confidence band rather than a binary verdict.
Data handling: GDPR compliant. UK and EU hosted. Submitted text is not stored after the scan completes.
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 IsItAI 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 IsItAI 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 IsItAI wins
- No conflict of interest. QuillBot's parent sells the paraphrasing tool built to defeat AI detectors, so its detector grades work its own product is designed to disguise.
- Passage-level highlighting, a confidence band and an API. QuillBot's detector is a free add-on with no API.
- Wider language coverage at 30 versus 3, and a no-storage GDPR policy versus QuillBot storing submissions for product improvement.
Where QuillBot AI Detector wins
- Free and unlimited checks for quick casual passes.
- Sits next to QuillBot's paraphraser and grammar tools that students already use.
- No signup needed for a fast one-off check.
Which one should you pick, IsItAI or QuillBot AI Detector?
Pick IsItAI if you want an independent detector with flagged passages, a confidence band and no storage. Pick QuillBot only for a free, casual gut-check, keeping in mind the same company sells the paraphraser built to beat detectors, which is the clearest example of that limit.
Frequently asked questions
Is IsItAI free?
5 scans/day 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, IsItAI or QuillBot AI Detector?
Pick IsItAI if you want an independent detector with flagged passages, a confidence band and no storage. Pick QuillBot only for a free, casual gut-check, keeping in mind the same company sells the paraphraser built to beat detectors, which is the clearest example of that limit.
Try IsItAI free
5 free scans a day. No credit card. UK hosted and GDPR compliant.
Sources and further reading
- IsItAI homepage
- Pricing
- How it works
- 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