Don’t Train Your Models
on Bad Data

GPTZero is the first and leading AI detector that allows you to identify specific content in a document or text that has been generated by a large language model (LLM), such as ChatGPT. Founded in January 2023, GPTZero has served over 10 million users to date and works with 100+ organizations in education, hiring, publishing, legal and more.

AI detectors work by looking for patterns in text that are more likely to have been written by a machine than a human. The most common factors they look for include:

• Perplexity: Is the writing obviously predictable?
• Burstiness: How much variation is there in the sentence length and style?
• Style: Is the tone and writing style overly generic or repetitive?

GPTZero uses its own proprietary model that takes hundreds of factors into consideration and boasts the highest detection accuracy in the industry.

Yes. Independent benchmarks, like our partners at Penn State’s AI Research Lab, and our own large-scale testing show that GPTZero is the most accurate AI detector, with a 99% accuracy rate when spotting AI-generated text vs. human writing, a false negative rate under 2%, and a false positive rate under 1%. This means we correctly classify AI writing 99 out of 100 times, and keep misclassification of text to an absolute minimum.

Unlike many competitors, GPTZero can reliably detect “mixed documents” (where human and AI writing are combined) with 96.5% accuracy rate. While no AI detector can ever truly be 100% perfect, we are committed to being a leader in responsible adoption of AI generation and AI detection technologies.

You can start using GPTZero straight away in 3 easy steps:

1. Paste Text or Upload Document: Paste in raw text or upload your file for review and press ‘Scan’. For scans over 10,000 characters, create a free account first.
2. See Your Results: GPTZero will suggest what percentage of your text is likely to be AI-generated and highlight the specific phrases it has detected.
3. Download our Chrome Extension for Google Docs and web: View AI detection and typing pattern metrics on any page, allowing you to spot AI-created content with ease.

GPTZero is the most trusted AI content checker in education, both for teachers and students who use GPTZero to guide conversations on academic integrity and writing improvement. GPTZero is used in over 3500 colleges and 100s of institutions. We also serve publishers, recruiters, copy-writers, marketers and businesses where authentic and quality writing truly matters.

No. GPTZero works across a wide range of AI language models, including but not limited to ChatGPT, GPT-5, GPT-4, GPT-3, Gemini, Claude, Llama, Deepseek, and AI services based on those models. Our detector is designed for the highest accuracy rate regardless of which model may have produced the text.

In our latest model release, we’ve updated the majority of our training data, including more AI documents from: OpenAI – GPT4.1,GPT4.1-mini, o3, o3-mini Gemini – 2.5 Pro, 2.5 Flash, 2.5 Flash-Lite Claude, Sonnet 4 as well as a few other models.

GPTZero fully supports English, German, Portuguese, French and Spanish with industry-leading accuracy. We are also constantly used in many other languages and in over 100 countries.

GPTZero is consistently rated the most accurate and reliable AI detector across various use cases.

• Reliability: In 2025, G2 ranked GPTZero the #1 most trusted and reliable AI tool, above Grammarly.
• Accuracy: GPTZero is the most accurate AI detector with 99% accuracy rates across diverse datasets, independently reviewed by AI labs at top institutions. Independent reviewers, including Tom’s Guide, testing all popular detectors named GPTZero the most accurate.
• Best Interpretability: GPTZero is the only detector that explains exactly why text is AI with natural language. GPTZero also has the most accurate sentence-level AI detection, with color-coded highlights on exactly where AI is used in an essay.

No AI detector is 100% accurate, and AI itself is changing constantly. Results should not be used to punish or as the final verdict. Accuracy improves with longer inputs (document-level results are stronger than paragraph or sentence-level) and is strongest on English prose.

GPTZero is the only AI detector de-biased for ESL (English Second Language) learners, which many competitors do not take into account. We repeatedly train our model to reduce false positive rate for ESL writing to 1%. We also monitor our datasets to transparently prevent any bias in AI detection training data.

Our model is trained on millions of documents spanning various domains of writing including creating writing, scientific writing, blogs, news articles, and more. We test our models on a never-before-seen set of human and AI articles from a section of our large-scale dataset, in addition to a smaller set of challenging articles that are outside its training distribution.

To see the full schema and try examples yourself, check out our API documentation.

Our API returns a document_classification field which indicates the most likely classification of the document. The possible values are HUMAN_ONLY, MIXED, and AI_ONLY. We also provide a probability for each classification, which is returned in the class_probabilities field. The keys for this field are human, ai or mixed. To get the probability for the most likely classification, the predicted_class field can be used. The class probability corresponding to the predicted class can be interpreted as the chance that the detector is correct in its classification. I.e. 90% means that 90% of the time on similar documents our detector is correct in the prediction it makes. Lastly, each prediction comes with a confidence_category field, which can be high, medium, or low. Confidence categories are tuned such that when the confidence_categoryfield is high 99.1% of human articles are classified as human, and 98.4% of AI articles are classified as AI.

Additionally, we highlight sentences that been detected to be written by AI. API users can access this highlighting through the highlight_sentence_for_ai field. The sentence-level classification should not be solely used to indicate that an essay contains AI (such as ChatGPT plagiarism). Rather, when a document gets a MIXED or AI_ONLY classification, the highlighted sentence will indicate where in the document we believe this occurred.

No. We do not store or collect the documents passed into any calls to our API. We wanted to be overly cautious on the side of storing data from any organizations using our API.

However, we do store inputs from calls made from our dashboard. This data is only used in aggregate by GPTZero to further improve the service for our users. You can refer to our privacy policy for more details.