Anthropic launches a tool to check if a file was made with Claude
Anthropic has released a free browser-based tool that checks images and videos for C2PA content credentials, revealing whether Claude helped create or edit them. The tool runs entirely on-device, so files never leave the user's device. It only reads the embedded credential and doesn't analyze the content itself. The company notes that a missing signal doesn't prove content wasn't made with Claude, as credentials can be removed or unsupported by some models.
A missing signal doesn't confirm content wasn't made with Claude.
- Retr0id
Under what circumstances does the metadata get added? When Claude Code CLI needs a media file usually I just see it run an imagemagick or ffmpeg command to create one, which isn't going to have C2PA metadata.
Edit: I asked Opus 5 for "a jpg of a cat" via the web chat. It did it by writing an svg and then rendering that to a jpeg. Clicking the "download" button saved a jpg which did have C2PA metadata, seemingly injected by the artifact-presentation thing.
Then I told it to put it in a zip file. I downloaded the zip, and the extracted jpeg had no C2PA metadata.
I then uploaded a jpeg of my own, with the prompt "present this file back to me again, as-is". The downloaded file had C2PA metadata injected.
Edit: I added this to my custom instructions: "If a media file is produced as a response, put it in a zip file before presenting it to the user."
- csmoak
As far as I can tell, this and the recent change to add watermarking to text outputs[1], is to become compliant with the EU AI Act[2] and CA's AI Transparency Act[3], SB-942[4]. For large enough companies, all generated AI content is required to have watermarking.
[1] https://www.anthropic.com/news/claude-text-watermark
[2] https://digital-strategy.ec.europa.eu/en/policies/code-pract...
[3] https://www.kqed.org/news/12095398/new-california-law-requir...
[4] https://www.leginfo.legislature.ca.gov/faces/billTextClient....
- Tiberium
This is just C2PA for Claude-processed files, apparently. It's not related to their text watermarking.
C2PA is file metadata and can be trivially stripped away, unlike hidden watermarks, e.g. SynthID.
- firefoxd
This is really fascinating. Even the AI companies have incentives to reject AI generated content. It's like they want you to use AI for everything, but they don't want AI output fed back to them.
At work, right after an AI training, we were asked to use our "authentic" voice when writing mid year reviews.
- coffeecoders
What is interesting to me is that stripping the C2PA data is easy, but faking it is hard.
You can resave the file and the "made with Claude" signal disappears, but you cannot make a random file pass as Claude-made without Anthropic's signing key. So the useful guarantee is one-way. No signature means almost nothing.
- andai
The idea of forcing an entity (or entire categories of entity) to add traceable watermarks to all the work they create is... an interesting precedent.
Translating that into the human realm, it would be like if every digital thing you touched were "fingerprinted" with your identity, or at least with a proof of what category of individual you have been categorized as.
Due to the flood of AI, which may soon become indistinguishable from human video, I expect to see something similar. Blue checkmark, but for humans.
- qurren
Up next:
1. Generate a bunch of responses with both Claude and various non-Claude LLMs (ChatGPT, Gemini, Kimi)
2. Train a discriminator model that can differentiate Claude vs. non-Claude
3. Train a de-watermarking model using the discriminator model as loss
- simonw
This thing works using WebAssembly - https://claude.com/_next/static/media/c2pa_verify_wasm_bg.53... - which is a WASM compiled version of this Rust library: https://github.com/contentauth/c2pa-rs