OpenAI will begin adding an invisible watermark to eligible text generated by ChatGPT and Codex in the European Union (EU), as the company moves to comply with transparency requirements under the EU’s AI Act.
It does not insert hidden characters or additional watermark-specific tokens. Instead, the statistical pattern in the model’s word choices can subsequently be analysed by a detector. Editing also significantly weakened the signal.
Separately, from October 5, API customers worldwide can opt in to text watermarking for select models, OpenAI said. The move comes as Article 50(2) of the EU AI Act requires providers of generative AI systems to ensure that AI-generated or manipulated content, including text, is marked in a machine-readable format and detectable as artificially-generated or manipulated. Section 1 of the Code deals with the marking and detection of AI-generated content by providers and Anthropic, Google, Meta, Microsoft, Mistral and OpenAI have signed this section of the Code. In an evaluation of 400-token passages, replacing 10% of words with synonyms reduced detection from about 92% to 66%, while replacing 25% of words reduced detection to about 17%, according to OpenAI.
The company said the rollout would take place over the coming weeks and apply to eligible users across all ChatGPT and Codex plans in the EU. It said it was not making text watermarking a global default at launch. OpenAI said its text watermarking technology, called textGrain, adds an invisible statistical signal to the model’s choice of words.
OpenAI plans to make textGrain available as open-source technology, saying this could allow others to build on the approach and help improve text watermarking.
