Claude watermark guide
How Claude Watermarking Works
Claude’s text watermark uses low-stakes word-selection choices to create a statistical pattern. Nothing is added to the response: there are no hidden characters, secret strings, or extra tokens.
A probabilistic signal
When several plausible next words preserve meaning, watermarking changes the randomness used to choose among them. A keyed detector can test whether many choices are consistent with that pattern.
Limits of the signal
Anthropic says short samples provide less information and factual or exact text offers fewer choices. A watermark indicates likely Claude involvement; it does not establish authorship or ownership.
Check your Claude text
Inspect every detectable hidden character locally, then clean only the artifacts you select.
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Published August 2026 · Updated September 1, 2026