The Writefull GPT Detector is a free tool that lets users determine whether a text was generated by GPT-3, GPT-4, or ChatGPT. It gives you a probability score that indicates how likely it is that the text was generated by AI. The tool is safe and secure because user information is encrypted and not stored. API access is also available by request. Accuracy Test: The Writefull GPT Detector received an overall score of 78%, placing it among the most accurate free tools available. It accurately detected all GPT-3.5 and GPT-4 texts and did not misidentify any human-written text as AI-generated. It also outperformed expectations when detecting AI content that had been combined with human-written text or altered using paraphrasing tools.