OpenAI's textGrain watermark: phased rollout to meet EU text provenance rules

Our approach to EU text provenance rules

OpenAI published textGrain, its text watermarking plan for the EU AI Act. From today, API customers worldwide can turn it on for some models; it stays off by default. In the coming weeks, eligible ChatGPT and Codex text output in the EU will carry an invisible watermark, and the detector opens to approved researchers and professional organizations by application only.

Why it matters: OpenAI disclosed that detection rates fall after synonym substitution, so text edits weaken the provenance signal and results cannot be used to conclude text was human-written.