Claude’s Invisible Ink: What Anthropic’s AI Watermark Actually Marks
Imagine two very different ways of proving where a letter came from. One is invisible ink woven into the paper’s fibers during manufacturing — undetectable unless you know the exact chemical to reveal it. The other is a wax seal stamped on the envelope, showing who sent it and whether it’s been opened since. Anthropic’s new marking system for Claude works roughly the same way: one mechanism is baked into the text itself and invisible to the eye, the other is a signed label attached to certain files. They are not the same thing, they don’t fail in the same way, and confusing them is the easiest mistake a curious reader can make.



