Anthropic starts invisibly watermarking Claude's text and image outputs

Anthropic said Claude models launched on or after 2 August 2026 embed an imperceptible, machine-readable watermark directly into generated text, alongside signed C2PA provenance metadata attached to generated files such as images. The company said the change applies worldwide across the API, Claude Code and cloud partners, and framed it as fulfilling commitments under Article 50 of the EU AI Act’s Code of Practice on transparency, which it had signed.

Anthropic’s support documentation describes the text watermark as designed to travel with the content when copied and pasted elsewhere, and to survive light editing, but said it would degrade if text is heavily rewritten, paraphrased, translated or mixed into other writing. File-level C2PA metadata is similarly fragile, and can be lost through format conversion, re-saving or screenshots. Models released before 2 August do not carry the feature yet; Anthropic said it was working to retrofit it. Detection tooling for third parties to check content for the marks was described as forthcoming, with technical documentation to follow.

The move follows OpenAI’s adoption in May of Google DeepMind’s SynthID watermark for images paired with the same C2PA standard, making watermarking-plus-provenance-metadata the emerging norm among major labs facing the same EU transparency deadline. As with OpenAI’s rollout, Anthropic cautioned that the signals indicate Claude’s involvement in producing content rather than serving as proof of full authorship, and that a determined user can still strip both marks.

The claim rests on Anthropic’s own support page, which carries no publication date of its own; the 11 August date reflects when independent outlets first reported the update, and this entry should be revisited once Anthropic publishes dated technical documentation or detection tooling.