OpenAI is introducing text watermarking in the European Union to comply with the EU AI Act's transparency rules, which took effect on August 2, 2026, and require AI providers to label generated text

From the articleOpenAI will start watermarking ChatGPT’s text in the EUAlso in OpenAI will watermark ChatGPT text in the EU but makes it optional for API users worldwide, OpenAI is adding text watermarking in ChatGPT and Codex