Claude’s watermark knows AI was used. It doesn’t tell if you wrote the essay, it wrote the essay or just fixed a comma

Anthropic confirmed this week that it has started embedding invisible, machine-readable watermarks into everything its Claude AI models generate, a global rollout triggered by new transparency rules under the European Union’s AI Act. The change reaches users everywhere: on the web, the mobile app, coding tools and cloud platforms, regardless of whether the EU rules apply to them directly.

The shift raises an obvious question: what does a watermark actually prove, and what happens once AI text is edited or blended with a person’s own writing?