Anthropic adds invisible text watermark to Claude outputs starting Nov 3
petesena · x · 2026-10-31
- Anthropic has emailed customers that starting November 3, 2026, a text watermark will be applied to outputs from Claude Mythos 5, Claude Opus 4.7, Claude Opus 4.6, and Claude Sonnet 4.6, with Amazon Bedrock rollout following a few days later; newer models like Claude Opus 5.5 already carry it.
- The watermark is an imperceptible pattern in word choice: it doesn't change meaning, quality, pricing, or speed, and contains no info about the user or their conversations — it only marks that Claude touched the text, even a quick proofread counts.
- Per the poster, it survives copy-paste and some editing, and for now only regulators, journalists, fact-checkers, and researchers can check for it. Brands relying on Claude for copy should assume AI involvement is now detectable.
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