OpenAI to watermark ChatGPT and Codex text in the EU, off by default elsewhere
OpenAI said it will add an invisible textGrain watermark to eligible ChatGPT and Codex text in the European Union over the coming weeks for users on all plans, to comply with the EU AI Act's transparency rules; API customers worldwide can opt in starting today, with watermarking off by default. The method embeds a statistical signal in the model's word choices rather than visible characters, and OpenAI published a technical report co-written with University of Pennsylvania and Yale researchers, saying it saw no meaningful benchmark differences with watermarking on. Detector access is initially limited to approved researchers and expert organizations, and OpenAI says it plans to open-source the technology, while cautioning that detection falls to about 80% on 200-token passages and weakens sharply after synonym edits.