GPT-2 Output Detector
The original open research detector, still useful as a transparent baseline.
The GPT-2 Output Detector is the research demo that started public AI detection. Built on a RoBERTa classifier trained to separate GPT-2 samples from human text, it runs free in the browser with no account and returns a simple real-versus-fake probability. Its value in 2026 is not raw accuracy, because it was never trained on GPT-4-class or Claude-class output and it under-flags modern models badly. Its value is transparency: the model, the training method, and the limits are all public, which makes it a useful teaching tool and a sanity check when a commercial detector returns a score you cannot explain. Treat it as a historical baseline, not a verdict. If you need a decision you can defend, pair it with a current detector such as Originality.ai or GPTZero and never rely on it alone for anything consequential.
| Best for | Researchers, teachers, and anyone wanting a transparent baseline |
|---|---|
| Pricing | Free |
| Category | AI Detectors |
Highlights
- Free, no signup
- Fully open method
- Weak on modern models