GPTZero

GPTZero is an AI-content detector created by Edward Tian, then a Princeton student, and released in early 2023 as ChatGPT swept through classrooms. It estimates how likely a passage was machine-written by measuring perplexity (how predictable the word choices are) and burstiness (how much sentence complexity varies) — AI text tends to be smoother and more uniform than human writing.

It has become one of the best-known names in a crowded field that includes Turnitin’s AI detector, Copyleaks, Originality.ai, and Winston AI. GPTZero’s pitch is breadth of access: a free web checker, browser extensions, an LMS-friendly batch mode, and an API, all aimed at teachers, publishers, and hiring teams who need a quick read on whether text came from ChatGPT, Claude, or Gemini.

Importantly, GPTZero itself frames its scores as signals, not verdicts — a stance worth remembering given how consequential a false accusation can be.

Key Features

• Detects output from ChatGPT, Claude, Gemini, and other major models
• Sentence-level highlighting of likely AI-written passages
• Perplexity and burstiness scoring with a human/AI/mixed verdict
• Batch file upload for grading or reviewing many documents
• API and LMS integrations for institutional workflows
• Writing-analysis and source-checking add-ons

Pricing

• Free: a monthly character/word allowance, good for occasional checks
• Essential (~$10/month): higher limits, batch uploads
• Premium/Pro (~$15–24/month): large monthly volume, advanced features
• Organization/Enterprise: custom volume and integrations

Best For

Teachers, professors, editors, and HR reviewers who want a fast, accessible first-pass check on whether a submission was likely AI-generated.

Limitations

No AI detector is reliable enough to punish someone on its word alone. GPTZero can flag genuine human writing as AI (a documented risk for non-native English writers) and can miss text that has been paraphrased or run through a humanizer. Treat it as one input alongside human judgment, not as evidence.