GPTZero

GPTZero was one of the first widely adopted AI detectors, released in early 2023 by Edward Tian. It analyzes text using two primary signals: perplexity (how predictable the text is to a language model) and burstiness (how much sentence length and complexity varies). The combination of both metrics gives it more nuance than single-signal detectors.

GPTZero reports results at both the document and sentence level, highlighting specific passages it considers likely AI-generated. This granular view makes it useful for editing — you can target the flagged sentences specifically rather than rewriting the whole document. It has become a standard tool for teachers, editors, and content platforms trying to enforce human-writing policies.

Like all detectors, GPTZero makes probabilistic judgments and is not infallible. Its false positive rate on technical and academic prose is non-trivial. For users testing humanized content, GPTZero is typically one of three detectors to check alongside Turnitin and Originality.ai — Coda One's AI Detector aggregates scoring signals from multiple detection approaches to give a more reliable overall read.