GPTZero is a software tool built to determine whether a piece of text was written by a human or generated by an AI model such as ChatGPT. Created in January 2023 by Princeton University student Edward Tian, along with co-founder Alex Cui, the tool arrived just weeks after ChatGPT’s public launch, when teachers and institutions had no reliable way to tell AI-written work from student writing. In short, GPTZero scans a document and returns a probability score indicating how likely it is that the text came from an AI system rather than a person. It has since grown from a weekend coding project into a widely used platform serving education, publishing, hiring, and legal organizations.
What Is GPTZero Used For?
GPTZero is used mainly to detect AI-generated text in academic and professional settings. Teachers use it to check whether student essays were written by ChatGPT or similar tools, while publishers, recruiters, and legal teams use it to verify the authenticity of submitted writing.
Beyond detection, the platform has expanded to include plagiarism checking, grammar review, and hallucination detection for AI-generated content. According to the company, GPTZero has served millions of users and works with more than 100 organizations across sectors that rely on original written work.
Who Created GPTZero?
GPTZero was created by Edward Tian, who was a Princeton senior majoring in computer science with a minor in journalism when he built the tool. Tian had previously researched AI-generated language detection at Princeton’s Natural Language Processing Lab, which gave him a head start once ChatGPT raised urgent questions about academic integrity.
Alex Cui joined as co-founder shortly after the initial launch, and the two had been friends since high school. The company grew quickly, reaching profitability within its first year and a half and raising a $10 million Series A round in 2024 led by venture firm Footwork.
How Does GPTZero Detect AI Writing?
GPTZero detects AI writing primarily by analyzing two linguistic properties: perplexity and burstiness. Perplexity measures how predictable a piece of text is to a language model; text that closely matches common AI-generated patterns tends to score lower, since AI models favor statistically likely word choices.
Burstiness measures variation in sentence structure and length across a document. Human writing tends to mix short and long sentences unevenly, while AI-generated text often shows more uniform rhythm and phrasing. GPTZero combines these signals, along with additional pattern analysis trained on large sets of human and AI-written text, to produce a document-level and sentence-level probability score.
Is GPTZero Accurate?
No AI detection tool, including GPTZero, is perfectly accurate, and false positives can occur, particularly with non-native English writing or heavily edited text. The company has continued refining its models since 2023 to reduce these errors as AI writing tools have grown more sophisticated.
Because detection scores are probabilistic rather than definitive, most educators and institutions use GPTZero as one input among several, rather than as sole proof of AI use. Combining detection results with class context, writing history, and direct conversation with the writer remains the recommended approach.
What Happened to GPTZero in 2026?
In June 2026, GPTZero was acquired by Superhuman, the company behind Grammarly, according to reporting from Business Insider. At the time of the acquisition, GPTZero was reported to be valued at 88 million dollars, with more than 19 million users and 30 million dollars in annual recurring revenue.
Both co-founders, Tian and Cui, joined Superhuman as part of the deal. The acquisition brought GPTZero’s AI detection technology under the same umbrella as Grammarly’s writing tools, positioning the combined company to address both AI writing assistance and AI detection within one platform.
How Is GPTZero Different From Turnitin?
GPTZero and Turnitin both offer AI detection, but they differ in origin and focus. GPTZero was built specifically as an AI text detector from the start, while Turnitin, a long-established plagiarism detection company, added AI detection features to its existing product after ChatGPT’s release.
GPTZero has also broadened into a fuller writing integrity suite with plagiarism, grammar, and hallucination checks, while Turnitin remains primarily rooted in academic plagiarism screening with AI detection as an added layer. Institutions often choose based on existing contracts, since many schools already use Turnitin for plagiarism checks separate from AI detection.
Conclusion
GPTZero started as a student project responding to ChatGPT’s sudden rise and has become a widely adopted tool for identifying AI-generated writing through perplexity and burstiness analysis. Its 2026 acquisition by Superhuman marks a new chapter, merging AI detection with mainstream writing assistance software. For anyone evaluating written content in education, hiring, or publishing, understanding how GPTZero works helps set realistic expectations about what AI detection can and cannot confirm.
FAQs
What is GPTZero used for?
GPTZero is used to detect whether text was written by an AI model like ChatGPT. Teachers, publishers, and employers use it to check the authenticity of essays, articles, and applications. It also offers plagiarism checking, grammar review, and hallucination detection for AI content.
Who owns GPTZero?
As of June 2026, GPTZero is owned by Superhuman, the company behind Grammarly, following an acquisition reported by Business Insider. GPTZero was originally founded by Edward Tian and Alex Cui in January 2023 and operated independently before the acquisition.
Is GPTZero free to use?
GPTZero offers a free version with basic AI detection features, alongside paid plans that unlock higher word limits, batch scanning, and additional tools like plagiarism and grammar checks. Pricing and feature tiers may change, so checking GPTZero’s official site is recommended for current details.
Can GPTZero detect ChatGPT specifically?
Yes, GPTZero was originally built to detect ChatGPT-generated text and has since expanded to detect output from other large language models, including GPT-4, Bard, and LLaMA. It analyzes writing patterns common across these models rather than relying on a single AI system’s fingerprint.
Does GPTZero give false positives?
Yes, like all AI detection tools, GPTZero can occasionally flag human-written text as AI-generated, especially with non-native English writing or edited content. Because of this, most experts recommend using detection scores as one factor rather than definitive proof of AI use.
