GPTZero is an artificial intelligence detection software developed to identify artificially generated text, such as those produced by Large language models. It was created to address concerns about academic dishonesty and the misuse of AI writing tools. While praised for its efforts to prevent plagiarism, many news outlets have criticized its false positive rate, which can be harmful in academic settings.
The software analyzes text to determine the likelihood of AI authorship, providing classifications at the document and sentence level with confidence scores. It has evolved from its initial mechanism based on linguistic qualities to a more advanced deep learning classifier, and has been adopted by educators, hiring managers, and other professionals.
History
GPTZero was developed by Edward Tian, a Princeton University undergraduate student, and launched online in January 2023 in response to concerns about AI-generated usage in academic plagiarism. In its first week, the tool experienced 30,000 uses, which led to a crash; it was supported by the web app company Streamlit, who allocated more server resources in response. In May 2023, GPTZero said it raised over 3.5 million dollars in seed funding.
By July 2024, it had 4 million users, compared to 1 million one year earlier. In summer 2024, GPTZero raised $10 million in Series A round funding. In September 2024, GPTZero announced an authorship tracking software that enables users to compile and share data about their writing process, such as copy/paste history, number of editors, and editing duration, in an effort to move away from an all-or-nothing paradigm around AI writing towards a more nuanced one.
Superhuman, a company developing AI-powered email software for productivity and workflow automation, announced it had acquired GPTZero in June 2026. Superhuman planned to integrate GPTZero into its Superhuman Go AI assistant, while GPTZero said the acquisition would help place its tools in products where users already read and write.
Mechanism
When it first launched, GPTZero used qualities it termed perplexity and burstiness to attempt to determine if a passage was written by an AI. According to the company, perplexity measured how random the text in a sentence is and whether the sentence construction is unusual or surprising for the language model. Texts with language more chaotic or unfamiliar to language models - that is, likely to perplex the model - were deemed more likely to be written by humans. Burstiness, in contrast, compared sentences with each other to determine their similarity. Human text is more discontinuous, meaning humans tend to write with more sentence variation than AI.
In autumn 2023, GPTZero stopped using perplexity and burstiness and switched to an end-to-end Deep learning based classifier trained on a dataset of millions of documents from domains such as creative writing, scientific writing, and news articles. The classifier predicts if a text is entirely human-written, entirely AI-generated, or a mix of both, such as a human-written text polished by AI. It provides classification results at the document and sentence level and assigns a confidence score to its predictions.
As of September 2025, free tier users can scan 10,000 words a month, with a maximum of 10,000 characters per scan.
Use cases
The academic community has attempted using GPTZero to tackle concerns about AI-generated content for plagiarism. Educational institutions, including Princeton University, have discussed the use of GPTZero to combat AI-generated content in academic settings, with mixed opinions. In October 2023, GPTZero partnered with the American Federation of Teachers.
By 2024, Tian reported that GPTZero also received a lot of adoption with hiring managers, with recruiting and cover letter analysis.
Efficacy
In a March 2023 paper titled "Can AI-Generated Text be Reliably Detected?", computer scientists Vinu Sankar Sadasivan, Aounon Kumar, Sriram Balasubramanian, Wenxiao Wang, and Soheil Feizi from the University of Maryland demonstrated empirically and theoretically that several AI-text detectors are not reliable in practical scenarios.
Tech website Futurism tested the tool and said that while the results were impressive, based on its error rate, teachers relying on the tool would end up falsely accusing nearly 20 percent of innocent students of academic misconduct. The Washington Post noted in August 2023 that GPTZero suffers from false positives, emphasizing that even a small false positive error rate means that some students could be wrongly accused. In September 2025, Business Insider compared the tool to seven other AI detection tools and called GPTZero the "best free AI detector."