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Ars Technica · AI· Samuel Axon·· 2026-10-0765

OpenAI will watermark ChatGPT outputs by default—but only in the EU

OpenAI will watermark ChatGPT outputs by default—but only in the EU

Brief overview

OpenAI will default to adding watermarks to text generated by ChatGPT in the European Union region, aiming to comply with the EU AI regulation requirements that took effect in August. The EU-specific watermark technology is called textGrain, which uses proprietary algorithms to embed specific patterns into word selection that are difficult for humans to detect, requiring a dedicated detector to identify, but OpenAI acknowledges that it may be circumvented by individuals with basic technical skills. The company states it will provide detectors to a limited number of researchers and institutions and will establish an application process for other institutions to join.

Article

OpenAI will begin automatically watermarking text generated with ChatGPT in the European Union, the company has announced. It will also offer the watermarking feature in other regions, but it will be off by default outside of the EU.

The move in Europe is driven by a need to comply with the EU AI Act, which took effect in August. It requires marking content produced by AI models in a way that another tool can detect. Unfortunately, there is still no completely effective and reliable way to do that. A few standards already exist, like SynthID and the C2PA project, but they are relatively easy to circumvent for anyone with basic know-how.

The same is likely true for OpenAI's watermark. Its method is proprietary; the company calls it textGrain, and has published a technical paper explaining how it works. But in general, it works like other LLM watermarking tools we've seen in the past: It puts patterns in the word choices that are not clear to a human reader and that don't meaningfully change the general quality of the output, but that someone with a key can use a specialized detector to find. OpenAI says it will be giving access to the detector to a limited number of researchers and organizations and providing a request-for-approval process for others to be added over time.

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Source: Ars Technica · AI · arstechnica.com