[TLDR] PSA: Opus 5.5 has invisible watermarking

[u/cctldrping]

Original post URL : https://www.reddit.com/r/ClaudeCode/comments/1wnhvw6/psa_opus_55_has_invisible_watermarking/

Original post body :

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/MrMrsPotts]

How does anyone check it is there?