Anthropic launches a tool for checking whether files “came from Claude”

Anthropic has posted a tool on its website that lets you check whether Claude had a hand in creating a given file. It runs right in the browser: the user drags a file into the window, and the check happens locally — the company says the file never leaves the device, isn't stored, and isn't used for any other purpose. The tool reads only the embedded metadata, not the content itself.

What exactly gets checked

Anthropic marks the content it produces in two ways. Texts — a draft letter or essay, say — get a watermark woven into the fabric of the writing itself. Files (images, audio, video), meanwhile, are given a so-called content credential when downloaded: a small, cryptographically signed note in the metadata indicating that the file was made or processed with Claude's involvement.

The tool that has been released recognizes only this content credential. It shows whether Claude was involved in producing the file, but it can't determine whether Claude took part in creating the content itself, and it reveals no information about the user.

The C2PA industry standard

Underpinning it is the open C2PA standard — the same one used by camera makers and developers of image-editing software to record a shot's provenance. Any tool that supports C2PA can read such a note; if it points to Claude, the site will say so.

A wide range of formats is supported: images (JPG, PNG, GIF, WEBP, TIFF, HEIC, AVIF, SVG, DNG, JXL), video (MP4, MOV, AVI) and audio (WAV, MP3, M4A, FLAC) — up to 100 MB in size. Anthropic notes that similar tools are already offered by other model providers, including OpenAI and Google DeepMind.

And what about text

For detecting watermarks in text, the company has a separate Detection API. For now it's available only in a closed preview to select organizations — as, according to Anthropic, EU law requires.

The appearance of such tools fits a broader trend: as generative models spread, the question of where content comes from grows ever more pressing, and vendors are trying to offer at least some means of tracking it. That said, it's worth understanding the limitations: C2PA metadata is tied to the file and easily lost — the moment you take a screenshot, for instance, or re-save an image with a third-party editor.

Source: Lobsters