We’ve written an FAQ to answer some of the questions we've received about watermarking.
In summary:
• We’re implementing watermarking to comply with the EU AI Act. Other major model developers have signed the same Code of Practice and will also be implementing watermarking;
• Our watermarking method doesn’t have any practical impact on the quality or content of Claude’s outputs;
• The difference between watermarked and un-watermarked text will not be distinguishable to readers;
• Nothing is added to the text and there are no hidden characters;
• Watermarking doesn’t require extra tokens, and will not be more expensive;
• Watermarks can’t be traced to a specific person, organization, or chat.
Read more: https://t.co/G76iUOJ7Hu
sounds like Anthropic’s watermarking is MUCH more interesting than hiding invisible Unicode, as most people assumed.
the watermark is baked into the token selection itself!
at a high level:
normal Claude:
context → probability cloud + random sampling → token
watermarked Claude:
context → probability cloud + key/context-derived sampling → token
Anthropic confirmed they’re using a version of Google DeepMind’s SynthID-Text.
instead of pushing Claude toward some special set of words, the watermark changes the source of randomness used to choose between words Claude already considers plausible.
do that once and there’s basically nothing to see.
do it across hundreds or thousands of tokens and those choices accumulate into a statistical signature that someone with the key can recognize.
so the watermark isn’t attached to Claude’s output.
the output IS the watermark.
that’s why copy/pasting doesn’t remove anything. you copied the carrier signal itself. 🧬