OpenAI adds invisible text watermarking to ChatGPT and Codex in the EU

OpenAI is rolling out an invisible, machine-readable 'textGrain' watermark on ChatGPT and Codex text, initially for EU users. It says the method matched or exceeded alternatives like Google DeepMind's SynthID for text, and that benchmark performance is similar with and without it. OpenAI notes it does not guarantee detection, and editing text can weaken the marks.

Why it matters: The EU AI Act is now forcing labs to ship provenance features, and Anthropic made a similar move in August, so regional regulation is becoming a de facto standard-setter. Watermarks that degrade under light editing limit their value for catching misuse, and the API opt-out leaves a large gap.