After months of heads-down grinding, I’m proud to share that the @GPTZeroAI team has released the world’s most accurate AI detection model, GPTZero 4o. It’s called 4o because there are four zeros: we mark less than one in 10000 human texts as AI, evaluated across diverse passages of student writing. At the same time, we detect Claude Fable with 98.4% accuracy. We outperform Pangram in 3rd party benchmarks. Along the way, our research found major biases in the Pangram detector.