OpenAI adds opt-in text watermarking in the API and will watermark EU ChatGPT and Codex text

ChatGPTProduct changeConfirmed

API customers worldwide can now opt in to invisible text watermarking for select models; it stays off by default.

Over the coming weeks, OpenAI will add an invisible watermark to eligible ChatGPT and Codex text output for users on all plans in the EU only; it is not a global default.
OpenAI is taking applications from approved researchers and expert organizations for its text watermark detector, which is not public.

Who can use it: API: customers worldwide, opt-in, select models (not named). ChatGPT and Codex: eligible users on all plans in the EU. Detector: approved researchers and expert organizations, case by case.
When: Announced October 5, 2026. API opt-in available now; EU ChatGPT and Codex watermarking over the coming weeks, with no date given.

Read the official announcement for access details. Availability can depend on your plan, region or workplace settings.

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