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About Claude Watermark

Claude Watermark is a comprehensive tool for detecting and removing invisible artifacts left behind when copying text from Claude's chat interface. It scans for HTML class names containing 'claude', zero-width characters, byte-order marks, exotic spaces, and stylistic signals like em dashes and curly quotes, all of which can trigger detection by platforms like AO3. The checking and cleaning features run entirely in the browser with no account required and no data uploaded. For removing the deeper statistical watermark embedded in word choice, the tool offers a paid rewrite engine that passes text through a different model, a technique that Anthropic's own documentation acknowledges may prevent the mark from surviving. The project is open source, independently developed, and transparent about the limitations of watermark detection, notably that nobody outside Anthropic can verify their statistical watermark without the unreleased key.