Claude added AI watermarks. Now there's tool to remove them
What's the story
Cardano founder Charles Hoskinson has published a free tool that claims to remove invisible watermarks from Claude-generated content. The move comes just days after Anthropic added new features to its models that add watermarks to AI-generated content. The tool is designed to work with any text-based output generated by Anthropic's Claude models.
Technical approach
Tool removes 'Co-Authored by' tag from text
Anthropic's new feature adds watermarks at the model level, a move to comply with the European Union's AI Act transparency code.
The watermark isn't a hidden character string but a secret key that affects token sampling.
Hoskinson's tool removes the "Co-Authored By" tag from text, re-encodes images to remove embedded C2PA credentials, and uses a different model for content rewriting.
Functionality
Tool operates in 3 modes
The tool operates in three modes: Clean, which removes trailers predictably; humanize, which rewrites prose for a more natural sound; and orchestrate, which halts the process when Claude is being used.
However, it has a major limitation: if you run the rewrite through Claude or Gemini, the watermark will be added back.
The code of this tool carries very little of the watermark due to limited opportunities for word/phrase replacement in code syntax.
Ownership concerns
Hoskinson views his release as a warning sign
Hoskinson sees his release as a warning sign, not just a utility. He argues that the watermark and Claude co-author line could create future problems.
He interprets the co-authorship language as a condition users must satisfy before claiming ownership, suggesting that violating these terms could mean ownership is never transferred.
A published co-authorship line could also serve as evidence of joint authorship later on.
Licensing details
Code released under Apache 2.0 license
The code for Hoskinson's tool is released under the Apache 2.0 license, a permissive open-source license that permits copying, modifying, selling, or including the code in other products as long as original copyright and license notices are preserved.
It also includes a patent license which prevents Anthropic from using patents to stop people from creating and distributing modified versions of this code.
Twitter Post
The tool is called "Anthropies"
I'm creating a new skill that can be used with most LLMs to strip out the Anthropic watermark. I call it Anthropies (Anthropic Herpies). I've also included a legal argument about how watermarks and the co-authored by Claude can cause issues down the road https://t.co/6eNx4br1BZ
— Charles Hoskinson (@IOHK_Charles) August 16, 2026