IsItAI vs GPTZero: 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
GPTZero
US, 2023The original AI detector, popular with educators in the US.
- Pricing
- From $14.99/month (Essential)
- Free tier
- 10k words/month free
- API
- Yes
- Languages
- 7
Side by side
| Feature | IsItAI | GPTZero |
|---|---|---|
| Free tier | 5 scans/day free | 10k words/month free |
| Starting price | From £4.99/month | From $14.99/month (Essential) |
| Cost per 1k words | £0.05 (Pro plan equivalent) | $0.02 on Pro plan |
| API available | Yes | Yes |
| Languages supported | 30 | 7 |
| Founded | 2024 | 2023 |
| Country | UK | US |
| Primary audience | Educators, recruiters and content teams | US schools and universities |
| Best for | Teachers, students and recruiters who want a clear confidence score and source-passage highlighting | US educators familiar with the brand and its 'perplexity and burstiness' explanation |
| Known weakness | Smaller brand than US incumbents | Documented false-positive issues on non-native English writing in peer-reviewed studies |
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.
GPTZero
Method: Perplexity and burstiness analysis on a sentence-by-sentence basis. Founded by Edward Tian.
Data handling: US hosted. Stores submissions for model improvement unless on enterprise plan.
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 GPTZero.
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 GPTZero are vulnerable to this.
Where IsItAI wins
- Built and hosted in the UK with GDPR compliance. Student or candidate text never leaves the UK or EU.
- Lower entry price at £4.99/month versus $14.99/month for the GPTZero Essential plan.
- Returns a calibrated confidence band on the result page rather than a binary 'AI' or 'human' label.
Where GPTZero wins
- Larger brand recognition with US educators and a longer track record (founded early 2023).
- More generous free tier at 10,000 words per month versus 5 scans per day.
- Public methodology built around perplexity and burstiness with a long history of academic discussion.
Which one should you pick, IsItAI or GPTZero?
Pick IsItAI if you are a UK educator or recruiter and care about GDPR compliance. Pick GPTZero if you are in the US and your institution already references it. Both should be treated as a screening signal, not proof, especially for non-native English writers (see Liang et al. Stanford 2023).
Frequently asked questions
Is IsItAI free?
5 scans/day free
Is GPTZero free?
10k words/month free
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 GPTZero?
Pick IsItAI if you are a UK educator or recruiter and care about GDPR compliance. Pick GPTZero if you are in the US and your institution already references it. Both should be treated as a screening signal, not proof, especially for non-native English writers (see Liang et al. Stanford 2023).
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
- GPTZero homepage
- GPTZero pricing
- Liang et al. (Stanford, 2023): GPT detectors are biased against non-native English writers
- Sadasivan et al. (2023): Can AI-generated text be reliably detected?