Anthropic is adding invisible watermarks to text from new Claude models.

Because marking happens at model level, supported outputs carry it across Claude products, the API, Claude Code, and major cloud platforms worldwide.

The watermark is woven directly into generated text, allowing it to travel through copying and sometimes survive editing.

This is because, Anthropic signed the EU's voluntary Code of Practice on Transparency of AI-generated Content, whose measures help implement Article 50's legally binding marking requirement.

Claude models launched in the EU on or after August 2, 2026 support marking at launch, with supported output marked worldwide.

Supported SVG, PNG, and JPG files use signed C2PA provenance metadata, which can indicate Claude processing and whether that metadata was altered.

Anthropic's own detection support is still in development, with technical documentation forthcoming for users and third parties.

A detected mark cannot prove Claude originally authored the material, because Claude may have edited, translated, or summarized human-created content.

Missing marks prove little either, since heavy rewriting, short passages, older models, unsupported surfaces, or stripped file metadata can erase the signal.

For publishers and platforms, the system adds useful provenance evidence. Its practical value will depend on how resistant the text watermark is to paraphrasing once Anthropic publishes the detector and technical method.