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Anthropic is stamping a hidden watermark on every Claude output worldwide, and it “may persist through some editing”

Anthropic is implementing invisible watermarks on all outputs from its Claude AI models globally, starting August 2, 2026, to comply with the EU AI Act's transparency requirements. These watermarks are designed to persist through some editing and copying, with metadata also being applied to supported file formats. While Anthropic is rolling this out worldwide, the effectiveness of the watermarks, especially through editing and translation, remains to be fully tested, and verification tools are still forthcoming.