Anthropic · 2026-09-02 · notable
Claude Content Checker — see if a file carries Claude's signed credential
The Claude Content Checker is a free browser page that reads C2PA Content Credentials and reports whether a file was made or edited with Claude. It takes images, video and audio up to 100 MB, and the file never leaves your device.
A free in-browser page that reads Claude's C2PA Content Credential out of a file's metadata.
What is it?
Anthropic has put its Content Credential checker online at claude.com/check-content. Drop in a file and the page reports whether it carries the cryptographically signed note Claude attaches when it produces supported media. Images (JPG, PNG, GIF, WEBP, TIFF, HEIC, AVIF, SVG, DNG, JXL), video (MP4, MOV, AVI) and audio (WAV, MP3, M4A, FLAC) are accepted, up to 100 MB each.
How does it work?
The check runs inside the browser, so the file stays on your device and Anthropic never stores it. The credential follows C2PA, the open provenance standard camera makers and photo editors also use, and the checker reads only that embedded record — it does not analyse the pixels or the audio. A valid signature shows Claude was involved in producing the file, and whether the record was altered afterwards.
Why does it matter?
Anthropic began marking Claude output in August but shipped no public way to read the marks back, so a credential was only as useful as the tools that could see it. This checker closes that gap for files. Anthropic is clear about the limits: it reports the credential only, it cannot tell you whether Claude wrote the actual content, and it identifies no user. Text watermark detection stays restricted to eligible organisations.
Who is it for?
editors, moderators and teachers
Try it
https://claude.com/check-content