Copyleaks vs ZeroGPT: 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
Copyleaks
Israel, 2015Enterprise-grade detection with multilingual support.
- Pricing
- From $9.99/month (100 credits)
- Free tier
- Limited free credits
- API
- Yes
- Languages
- 30
ZeroGPT
France, 2023Free, fast, ad-supported detector popular with students.
- Pricing
- From $9.99/month (ad-free)
- Free tier
- Unlimited free (with ads)
- API
- Yes
- Languages
- 50
Side by side
| Feature | Copyleaks | ZeroGPT |
|---|---|---|
| Free tier | Limited free credits | Unlimited free (with ads) |
| Starting price | From $9.99/month (100 credits) | From $9.99/month (ad-free) |
| Cost per 1k words | $0.10 | Free |
| API available | Yes | Yes |
| Languages supported | 30 | 50 |
| Founded | 2015 | 2023 |
| Country | Israel | France |
| Primary audience | Enterprises and institutions | Students and casual users |
| Best for | Enterprise teams needing multilingual detection and integrations | Casual one-off checks where price is the main constraint |
| Known weakness | Pricier than competitors for low-volume users | Inconsistent results have been reported across runs on identical input |
How each tool works
Copyleaks
Method: Proprietary classifier with paraphrasing-resistance claims. Integrates with LMS and CMS platforms.
Data handling: Enterprise tier offers no-storage option. Default plan stores submissions.
ZeroGPT
Method: Web-based classifier. Free tier funded by display advertising.
Data handling: Stores submissions. Public retention policy is limited.
How accurate are AI detectors? What the research says
Two findings from independent academic research apply to almost every detector on this list, including Copyleaks and ZeroGPT.
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 Copyleaks and ZeroGPT 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 Copyleaks wins
- Proprietary classifier with paraphrasing-resistance claims and LMS and CMS integrations, built for teams.
- Enterprise tier offers a no-storage option, where ZeroGPT stores submissions with a limited public retention policy.
- More consistent, where ZeroGPT has documented reports of inconsistent verdicts on identical input.
Where ZeroGPT wins
- Unlimited free checks funded by ads, versus Copyleaks' limited free credits.
- Wider claimed language coverage at 50 languages versus 30.
- Matches Copyleaks' entry price at $9.99 per month for an ad-free tier, and both offer an API.
Which one should you pick, Copyleaks or ZeroGPT?
Pick Copyleaks for teams needing integrations, paraphrasing resistance, and a no-storage enterprise option. Pick ZeroGPT for free, casual one-off checks where cost is the only concern, accepting that its results can vary run to run on the same text. Treat either as a screening signal, not proof.
Frequently asked questions
Is Copyleaks free?
Limited free credits
Is ZeroGPT free?
Unlimited free (with ads)
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, Copyleaks or ZeroGPT?
Pick Copyleaks for teams needing integrations, paraphrasing resistance, and a no-storage enterprise option. Pick ZeroGPT for free, casual one-off checks where cost is the only concern, accepting that its results can vary run to run on the same text. Treat either as a screening signal, not proof.
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Sources and further reading
- Copyleaks AI content detector
- Copyleaks pricing
- ZeroGPT homepage
- Zapier independent roundup of AI content detectors
- 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?