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Anthropic’s Claude Will Add Watermarks to AI-Generated Text and Files<br>Anthropic joins a growing list of companies letting customers know if they're consuming AI content.

Alex Valdes

Ever since being admittedly fascinated by the Cambridge coffee webcam from the 1990s, I've written about VPNs, the NFL, smartphones, living wages, over/unders and everything in between. Read full bio

Alex Valdes

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August 17, 2026, 2:19 pm ET

5 min read

Anthropic is adding watermarks to files, images and even text created by its Claude AI models. James Martin/CNET

You might soon be able to know if something came from a human being or from Claude. Anthropic said this month that text and files generated by its family of AI models will be watermarked to let consumers know. The change will allow the company to comply with EU regulations governing the transparency of AI use.

The EU’s Code of Practice on Transparency of AI-generated Content requires companies that provide and deploy AI systems to inform customers when they are interacting with AI and to include watermarks on AI content. Consumers also must know when they’re exposed to deepfakes and emotion-recognition and biometric-categorization tools. Nearly 200 organizations have agreed to the measures, the European Commission said.

Watermarking — an authentication process that originated in Italy in the 13th century — is entirely different for AI content. The AI system can automatically embed markers in text indicating that the content originated from AI and not a human. Examples could be different spacing between words and numbers, word sequencing and other invisible signals that remain with the text even if the person copies and pastes it across different platforms. Readers can’t see these markers, but computer systems can.

In its announcement, Anthropic said Claude models launched on or after Aug. 2 would include watermarking. That includes content created by Claude through the API, Claude, Claude Code, Claude Cowork and Claude Tag. Watermarking will apply to all Claude-generated content wherever the AI system is offered, not just in the EU.

Anthropic said it would "soon" share details about how customers can check whether text was generated by AI.

AI transparency is a growing trend. Substack partnered with Pangram to let readers know how much, if any, a post was generated by AI. Suno recently announced changes to help listeners know if a song was created by AI. If LinkedIn customers suspect AI slop, they can let LinkedIn know. Spotify’s new feature, AI Persona, allows listeners and creators to know which music was created with AI.

How text will be watermarked

To boil down an otherwise complicated process, Anthropic said that text generated by Claude models will be detectable because of how the words are chosen. If there is enough text, the AI detection tool will be able to spot a pattern that only Claude models would use to generate the text.

Anthropic said that text watermarking would not lessen the quality of the content and that readers will not be able to tell the difference between watermarked text and non-watermarked text, without using the AI detection tool.

"In internal testing, we’ve seen no impact of watermarking on the content, level of creativity or readability of Claude’s text," the company said.

Anthropic said its tool is based on the SynthID system that Google is using to detect AI in text, images, video and audio. How SynthID detects AI in text content is described in a Nature paper published in 2024.

Read more : I Used Every AI Cheating App and Detector and Came to One Conclusion

The watermarks Claude adds to text will remain, even if the text is copied and pasted from text editors such as Windows Notepad or MacOS’s TextEdit. The marks...