Overview
- Anthropic began embedding an invisible, machine‑readable watermark in text from Claude models launched on or after Aug. 2, 2026, and is attaching digitally signed C2PA provenance to generated files.
- The watermark is text‑native: the model nudges word choices to create a faint statistical pattern that travels with copied text and can persist through light edits.
- Anthropic says a detected mark signals Claude processed the text but is not proof of sole authorship and that a missing mark does not prove human origin.
- Researchers and builders published proof‑of‑concept scrubbers within days and experts warn heavy editing, format changes, screenshots, or reprocessing can remove or break the signal.
- Users and developers have pushed back with subscription cancellations and legal and privacy concerns, and Anthropic says it will publish detection tools and a free API but has not released detection details or error rates yet.