IsItAI vs Grammarly 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
Grammarly AI Detector
US, 2009 (AI detector 2024)Detection layered onto Grammarly's writing assistant.
- Pricing
- Bundled in Grammarly Pro from $12/month
- Free tier
- Free tier with limits
- API
- No
- Languages
- 1
Side by side
| Feature | IsItAI | Grammarly AI Detector |
|---|---|---|
| Free tier | 5 scans/day free | Free tier with limits |
| Starting price | From £4.99/month | Bundled in Grammarly Pro from $12/month |
| Cost per 1k words | £0.05 (Pro plan equivalent) | Bundled |
| API available | Yes | No |
| Languages supported | 30 | 1 |
| Founded | 2024 | 2009 (AI detector 2024) |
| Country | UK | US |
| Primary audience | Educators, recruiters and content teams | Existing Grammarly users |
| Best for | Teachers, students and recruiters who want a clear confidence score and source-passage highlighting | Existing Grammarly users wanting a one-click sanity check |
| Known weakness | Smaller brand than US incumbents | English only and not the main product |
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.
Grammarly AI Detector
Method: Detector added 2024 inside the Grammarly editor. English only.
Data handling: Stores submissions per Grammarly's main privacy policy.
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 Grammarly 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 Grammarly 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
- A purpose-built detector with passage-level highlighting and a confidence band. Grammarly's detector was added in 2024 inside its editor and is not its main product.
- Multilingual at 30 languages versus English only.
- Has an API for bulk and automated checks, where Grammarly's detector has none, and does not store submissions after the scan.
Where Grammarly AI Detector wins
- One-click convenience for the many writers who already work inside Grammarly.
- Bundled into Grammarly Pro, so existing subscribers pay nothing extra.
- Sits in the same editor where the writing already happens.
Which one should you pick, IsItAI or Grammarly AI Detector?
Pick IsItAI if you need a real detector: flagged passages, a confidence band, multilingual coverage and an API, from GBP 4.99/month. Pick Grammarly's detector only as a convenience if you already pay for Grammarly Pro and want an English-only one-click sanity check. Grammarly's detector is English only, so it is no help on multilingual work.
Frequently asked questions
Is IsItAI free?
5 scans/day free
Is Grammarly AI Detector free?
Free tier with limits
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 Grammarly AI Detector?
Pick IsItAI if you need a real detector: flagged passages, a confidence band, multilingual coverage and an API, from GBP 4.99/month. Pick Grammarly's detector only as a convenience if you already pay for Grammarly Pro and want an English-only one-click sanity check. Grammarly's detector is English only, so it is no help on multilingual work.
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
- Grammarly AI checker
- 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?