GPTZero

An AI detection tool used by over a million users worldwide to identify content created by AI models. Best free AI detector - simply paste your text to instantly get an overall AI score and advanced sentence by sentence detection. GPTZero is a leading AI detector that identifies text generated by large language models like ChatGPT, GPT-4, Gemini, and Claude, and it helps users spot AI content in documents or online text with high accuracy. Founded in 2023 by Princeton grad Edward Tian, it has served over 10 million users across education, publishing, and business, focusing on preserving authentic human writing. GPTZero claims 99% accuracy in distinguishing AI from human text on benchmarks like RAID, with just 1% false positives, and it performs even better at over 99% on modern models like GPT-4, though real-world tests show it dips to 80-98% on mixed or edited content. It fully supports English, German, Portuguese, French, and Spanish with top accuracy, and users report solid results in over 100 countries for other languages too, though performance shines brightest on English prose. Just paste text up to 10,000 characters or upload a file like a PDF or DOCX on the free tier, hit scan, and see results with AI percentages and highlights; for longer scans or advanced features, sign up for a free account first. Teachers and students in over 3,500 colleges rely on it for academic integrity checks, while publishers, recruiters, and marketers use it to ensure original content in high-stakes writing. It catches output from a wide range including GPT-5, GPT-4, Gemini 2.5, Claude Sonnet 4, LLaMA, and Deepseek, with recent updates boosting detection for these advanced models.