OpenAI adds invisible text watermarks to ChatGPT
OpenAI launched textGrain, an invisible watermark baked into text from ChatGPT and Codex. The system nudges word choices against a hidden key to create a statistical signal that readers cannot see, but approved detectors can later flag. It identifies only that text was probably produced by an OpenAI model, not the user, account, or prompt behind it. API access is opt-in globally and off by default outside the EU rollout, while eligible EU ChatGPT and Codex users will get it automatically over the coming weeks.
- OpenAI says the EU rollout is tied to the requirement that generated text be identifiable in a machine-readable way under the EU AI Act.
- In evaluations at a 1% target false positive rate, detection reached about 95% for 400-token passages in content such as psychology, compared with about 80% for 200-token passages.
- OpenAI says watermarking did not meaningfully change benchmark results across tests including DeepSWE, GPQA Diamond, and BrowseComp when comparing watermarked and unwatermarked Astra outputs.
