Claude now embeds an invisible watermark into every piece of text it generates.

Anthropic just documented how it works. Two marks, both machine-readable:

Text: an imperceptible watermark woven into the words themselves. You can’t see it, and it doesn’t change meaning, quality, or readability.

Files (.svg, .png, .jpg): signed provenance metadata on the C2PA open standard, so you can tell if a file’s been tampered with.

The watermark is applied at the model level.

That means it shows up no matter where the text comes from: the API, Claude, Claude Code, Cowork, Claude Tag, and even when a supported model runs through AWS, Google Cloud, or Microsoft Foundry.

Models launched on or after August 2, 2026 mark from day one. Older models are getting it during a transition period.

Every sentence Claude writes for you now carries a signature you’ll never see.