OpenAI brings text watermarking to ChatGPT and Codex — EU first

OpenAI is starting to embed invisible, machine-readable watermarks into the text produced by ChatGPT and Codex. Over the coming weeks the feature, called textGrain, will reach users on every plan — but only inside the European Union. The company has no plans to make it a global default yet: a regional rollout gives it room to gather feedback and see how the technology behaves in the wild.

The driver is the EU's AI Act. Following the same logic, Anthropic announced its own watermarks back in August. Tellingly, both companies lean on a common foundation — Google DeepMind's SynthID for text. Even so, OpenAI claims its own textGrain "matched or exceeded" rival approaches, SynthID included.

What the mark can and can't do

OpenAI included benchmark scores showing that watermarked and unwatermarked text perform about the same — the mark doesn't degrade generation quality. But the company is quick to add a caveat: textGrain "does not guarantee reliable detection." A watermark does not verify accuracy, determine who owns the text, measure how much a human contributed, or prove human authorship.

For the API it works differently: starting today, customers worldwide can opt in to watermarked outputs for select models. That lets them decide how watermarking fits their own transparency obligations. In parallel, OpenAI is working with cloud partners so the marks also apply when its models are accessed through their services.

A detector not for everyone

OpenAI is not releasing its detection tool to the public. From today, approved researchers and expert organizations can apply — under the Code of Practice, access is granted case by case. The detector only reports whether an OpenAI watermark is present, without revealing the user's identity, prompts, or conversations. The reason for caution is mundane: a mark can be missed, and it can be flagged falsely where none exists.

As The Verge notes, the announcement did not please everyone — not all were happy to hear about the addition.

Source: The Verge