Overview

GPTZero is an AI content detector. It analyses text to estimate whether it was written by AI models such as ChatGPT, GPT-5, Claude, Gemini or Llama, or by a person, and also checks writing quality. It is widely used in education: the site says it has more than 20 million users and over 2 million educators, and it is the official AI detection partner of the American Federation of Teachers.

Detection

You paste text, up to 10,000 characters in the free scanner, and GPTZero classifies it. Examples on the site distinguish between pure AI, human, mixed AI and human, polished-by-AI and paraphrased-by-AI text. The newest model is called GPTZero-4o. The company claims 99.9% accuracy and cites independent benchmarking for its Advanced Scan; treat these as the company's claims.

Writing replay

In Google Docs, GPTZero can show video proof of the writing process. You can watch a document being written, see copy-and-paste events and check for unnatural typing patterns. Writers can use replay and human writing verification to prove their work is their own.

Other tools

A plagiarism checker looks for content copied from outside sources without attribution. Free grammar checking and feedback help improve writing, and an AI writing tutor gives feedback aimed at responsible writing habits. A Chrome extension runs AI detection in Gmail, Google Docs, Google Classroom and on social media. GPTZero integrates with learning management systems including Canvas and Google Classroom. An API for developers comes with ready-to-use code in 17 languages.

Pricing

There is a free scanner. Paid individual plans, with an annual discount, add premium features. A Professional Team plan includes 500,000 words per member a month, shared credits and unified billing, with a minimum of two seats and card payment; contact sales for invoices.

Things to consider

No AI detector is perfect. False positives can wrongly accuse students, and non-native English writers may be flagged more often, so never use a score as the only evidence of misconduct. Talk to the writer and look at drafts or replay instead. Check your institution's privacy rules before uploading student work.

GPTZero says it is used in more than 100 countries. Teachers can scan whole classes through the LMS integrations, and the writing report summarises the findings for each document.