GPTZero

GPTZero is one of the most widely used AI detection tools, particularly among educators and content teams. Founded in 2023, it analyzes text for low perplexity and low burstiness — the two primary statistical signals of AI-generated writing — and returns a percentage score indicating how likely the text was machine-generated.

GPTZero offers a free tier for individual scans and paid plans for institutional use. It is commonly used by teachers to screen student submissions, by editors to verify freelance content, and by SEO teams to audit published articles. The tool supports batch scanning and API access for integration into content workflows.

GPTZero's accuracy is reasonable for unedited AI output but degrades with heavily edited or humanized text. It also produces false positives on writing by non-native English speakers and on highly formulaic human writing (such as technical documentation). No detector is infallible, and GPTZero itself recommends using scores as one signal among many.

To reduce GPTZero scores, writers use humanization tools that increase perplexity and burstiness, manually edit AI drafts to add personal perspective and concrete examples, or combine AI drafting with substantial human revision. In standardized tests, purpose-built humanizers like Refinely Human consistently achieve sub-20% AI scores on GPTZero.