Paste any text below to check if it contains Claude's invisible watermark.
Claude's statistical watermark lives in word choice at the token level and can only be detected with Anthropic's private key — no third-party tool can read it. What this checker CAN do reliably is scan your text for hidden Unicode characters (zero-width spaces, joiners, variation selectors) that are sometimes used as invisible text watermarks or tracking marks.
If hidden characters are found, the checker lists exactly which ones and how many. If none are found, your text is clean of invisible markers. This does not rule out a statistical token watermark, which is undetectable without the model owner's key.
Watermark Detected: The text shows statistical patterns consistent with Claude's watermarking. This doesn't mean the text is entirely AI-generated — even AI-assisted text can carry the watermark.
No Watermark Found: The text doesn't show detectable watermark patterns. It may be human-written, or the watermark may have been removed through editing or rewriting.
Need to remove a detected watermark? Use our Watermark Remover.