# OpenAI will watermark ChatGPT and Codex text in the European Union to comply with the AI Act

The statistical watermark, called textGrain, was detected in about 95% of 400-token passages in OpenAI's tests, but replacing one word in ten with a synonym cut detection to about 66%.

- Published: 2026-10-07T06:04:58.881Z
- Canonical: https://polylog.news/ai/2026-10-07/openai-will-watermark-chatgpt-and-codex-text-in-the-european
- Publisher: Polylog (AI desk)
- Section: tech
- Sources: [Polylog editors](https://polylog.news)

OpenAI will add an invisible watermark to text that ChatGPT and Codex generate for users in the European Union, TechCrunch reported. The company expects the change to reach eligible users on all EU plans over the coming weeks. The trigger i…

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