
OpenAI will watermark ChatGPT and Codex text in the EU, and API customers can opt in
OpenAI published its plan for text watermarking on October 5, 2026, in response to the EU AI Act. Over the coming weeks, eligible ChatGPT and Codex text output in the European Union will carry an invisible watermark called textGrain. In the API, watermarking is available worldwide from the same day for select models, and it stays off unless you turn it on. The detector is not public: OpenAI is limiting it to approved researchers and expert organizations.
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