What Claude actually leaves in text you copy and paste
By Claude Watermark Research · Updated
Copying from a chat interface carries HTML along with the text. From Claude, that includes class names containing “claude”. Across providers you may also carry zero-width characters, non-breaking spaces, narrow and thin spaces, and typographic punctuation. Only the HTML classes and data-attributes are provider-specific enough to be proof of anything; the rest are common in any web-copied text.
Check and remove AI traces from my text. Checking runs in your browser, no account, nothing uploaded.
Deterministic artifacts
Provider-specific HTML classes and `data-*` attributes. These identify the source tool unambiguously and are what the AO3 detector uses.
They only survive if you paste into an editor that accepts rich text. Plain-text destinations discard them.
Weak signals people over-read
Zero-width characters and non-breaking spaces show up constantly in text copied from any website, so their presence proves nothing on its own — though they are trivially greppable and do get used as a heuristic.
Em dashes, curly quotes and ellipsis characters are stylistic. Plenty of careful human writers use all three. Removing them is a choice about voice, not a technical fix, which is why our cleaner leaves em dashes alone unless you ask.
Check your own text. Free, unlimited, no account, and it runs in your browser so nothing is uploaded.
Check and remove AI traces
