Anthropic has pledged to start marking Claude-generated text and images with machine-readable data, in an effort to comply with European rules for AI transparency. “Generated text will carry embedded watermarks, and generated files will include digitally signed provenance metadata where supported,” Anthropic says on a new Claude support page. The changes are invisible to human eyes, but will make it easier for people and online platforms to detect if content was generated by Claude models.

These updates are a future commitment rather than something that will go into effect immediately. New AI labeling and transparency obligations under the EU’s AI Act, which came into effect on August 2nd, include a four month compliance grace period for existing AI products that launched prior to that date. As such, Anthropic says new Claude models will mark AI-generated content from day one upon release, but support for its existing models is a work in progress.

The machine-readable marks will be applied globally to supported Claude models, including Claude Platform (API), Claude, Claude Code, Claude Cowork, and Claude Tag. Two different marking techniques are being used: for images processed by Claude, C2PA — a provenance metadata standard already embraced by Adobe, OpenAI, and Google — will be applied to supported files, but the process for marking Claude-generated text is much lighter on details.

According to Anthropic, an “imperceptible watermark” is woven directly into the text generated by Claude models without changing the meaning, quality, or readability of the chatbot’s response. Anthropic doesn’t name this watermarking system, but says those text watermarks will also be applied when Claude models are accessed through AWS, Google Cloud, or Microsoft Foundry.

“Because the watermark is part of the text, it will travel with the text when it’s copied and pasted elsewhere, and may persist through some editing,” Anthropic says on the Claude support page. “Watermarking will be applied at the model level, which means it will be present no matter which Claude product or surface the text comes from.”

Anthropic is also working to enable users and other third parties to detect watermarks and provenance metadata embedded into Claude-generated content, and says it’ll share details on this detection system in upcoming technical documentation. There are several tools already available that are designed to detect C2PA metadata, including Google’s Gemini chatbot, but it isn’t clear if those will work with Claude-generated files. I’ve asked Anthropic for clarification.

This is another step towards AI-generated text and images being clearly tagged across online platforms, and a potential win for folks who want to avoid consuming such content. Fanfiction readers have already been building more rudimentary detection systems to flag when Claude tools have been used in AO3 fanworks, but these marking systems can be applied far more broadly — if they work, that is.

C2PA data is known to be easily stripped out, sometimes even accidently when the media carrying it is uploaded to online platforms, and it’s unclear how robust Anthropic’s text watermarking solution is. Even the company itself is hedging that these marking systems are far from infallible, and that any content that lacks detectable marks could still originate from generative AI models.