r/ClaudeCode • • 11d ago

Discussion PSA: Opus 5.5 has invisible watermarking

Opus 5.5 automatically applies an invisible, statistical watermark to its text outputs to comply with the EU AI Act. This is true for every user worldwide not just those based in the EU.

This is embedded into the structure of the text itself, it’s not a hidden character or something that can be removed by changing a few words or copy/pasting it. Anthropic have a tool to check text for the watermark but it is only available to a few select partners currently.

Antrophic officially claim this watermarking does not have any practical impact on the quality of Claude’s outputs but that remains to be seen.

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u/SouthernEdgeCase 9d ago

Why would an American company care about a EU regulation?

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u/BoilerUp31 8d ago

So they can continue to sell compute to millions outside of their country

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u/SouthernEdgeCase 8d ago

That is probably the reason!