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A careful answer

Does Claude Watermark Text? What We Can Verify

Hidden Unicode characters are not evidence of a Claude statistical watermark, and this site does not fabricate a Claude score.

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Text watermark limitation

Claude’s described statistical watermark is not made from hidden Unicode characters. Until an official detection mechanism is released, this scanner reports only directly observable characters and artifacts.

Your text stays in this tab. No text, findings, or cleaned output is stored or transmitted.

Statistical watermarking is about token choices

Text watermarking research generally nudges the probability of selected next tokens, creating a pattern that a compatible detector can test across enough text. That pattern is fundamentally different from inserting zero-width spaces or special punctuation.

Editing, translating, shortening, or mixing text can weaken statistical signals. Reliable interpretation also needs the provider’s exact method and calibrated detector.

What Anthropic makes available

Anthropic’s public transparency material says it continues to explore watermarking. Until Anthropic publishes an official, supported Claude detection mechanism, third-party claims of definitive Claude detection should be treated skeptically.

Primary sources and further reading

For technical and policy detail, consult the C2PA specification, Content Authenticity Initiative developer documentation, Anthropic transparency material, Google DeepMind’s SynthID overview, and the European Commission’s AI transparency guidance.