Two old-school reference works are going up against a very modern tech product. Encyclopedia Britannica and its subsidiary, Merriam-Webster, have sued OpenAI, alleging the tech company used Britannica’s content to train AI models without permission. The lawsuit said OpenAI’s chatbot, ChatGPT, has copied Britannica’s copyrighted content to train its large language models.

“ChatGPT then provides narrative responses to user queries that often contain verbatim or near-verbatim reproductions, summaries or abridgements of original content, including [Britannica’s] copyrighted works,” the lawsuit alleges.

(Disclosure: Ziff Davis, CNET’s parent company, in 2025 filed a lawsuit against OpenAI, alleging it infringed Ziff Davis copyrights in training and operating its AI systems.)

The lawsuit said ChatGPT-based products’ summaries of Encyclopedia Britannica’s content cannibalize traffic, and that OpenAI reproduces “web publishers’ copyrighted content without authorization or remuneration.”

The lawsuit from Encyclopedia Britannica and Merriam-Webster continues a trend of content owners suing AI companies for copyright infringement. 

Anthropic and Meta last year won lawsuits under the fair use exception that allows them to use copyrighted content without creators’ permission. Britannica also filed a lawsuit against Perplexity last year, which is still pending.

In relation to the new lawsuit, an OpenAI spokesperson told CNET via email: “Our models empower innovation, and are trained on publicly available data and grounded in fair use.”

 Encyclopedia Britannica did not immediately respond to a request for comment.