Superhuman Inc., the company behind the Grammarly brand, has acquired GPTZero Inc., the startup known for its AI-writing detection tools. The price wasn’t disclosed. GPTZero’s technology flags AI-generated text, fake citations, made-up statistics and plagiarism. It also verifies source existence and offers an “AI Vision” social-feed scanner and a keystroke “Replay” feature that reconstructs how content was written. GPTZero launched in 2022 after ChatGPT’s debut and now claims 19 million registered users and about $30 million in annual recurring revenue. Founders Edward Tian and Alex Cui, along with roughly 30 employees, will join Superhuman. Before the deal, GPTZero had raised $13.5 million in venture funding, including a $10 million Series A in June 2024, and PitchBook valued it above $88 million. Superhuman will fold GPTZero into Superhuman Go, its AI assistant that works across more than a million apps and websites. The company already has its own detector, carried over from the Grammarly era, which tops the RAID benchmark of over 670,000 test samples. By combining two different detection models, Superhuman aims to reduce false negatives and false positives as AI-generated content climbs to roughly half of all new online articles.