OpenAI watermarks ChatGPT text in EU under AI Act — SkimNews
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- OpenAI will add an invisible watermark to text from ChatGPT and Codex in the EU to comply with the EU AI Act's transparency rules, which took effect August 2, rolling out over the coming weeks to all EU plans.
- The watermark, dubbed "textGrain," works by subtly shaping word choices so a detector can spot AI-generated text; OpenAI said it travels with copied text, does not identify users, and caused no meaningful change in model performance.
- OpenAI published a technical report co-written with University of Pennsylvania and Yale researchers describing a secret-key method that sorts next-word predictions across hundreds of nudges to make text detectable.
- OpenAI's own tests show the watermark is fragile: replacing just 10% of words with synonyms dropped detection accuracy from about 92% to 66%, and short passages, math answers, and translated text are harder to flag.
- OpenAI is restricting detector access to "approved researchers and expert organizations" and warned that a missing watermark does not prove human authorship, since text could be too short, edited, or generated by another company's AI.
- API developers worldwide can opt in to watermarking for select models starting today (off by default), but OpenAI is not making text watermarking a global default at launch.
- Anthropic began watermarking Claude text two months ago on a worldwide basis and faced user backlash from customers who argued they supplied the "instructions, context, decisions" while Claude was "the tool."
Why it matters: OpenAI is following the EU AI Act's August 2 transparency rules, but the company itself is telling users the signal is easily defeated — a 10% synonym swap cuts detection by 26 percentage points — and is locking detectors behind an approved-researcher gate rather than releasing a public tool, meaning the watermark functions more as a compliance checkbox than a reliable provenance system.
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