Who made this file, and has it changed since?

If the file carries Content Credentials that say so, yes — this reports it prominently, along with the model that made it where the manifest names one. But the absence of a credential is not evidence that something is real. Most files on the internet carry no manifest at all, and metadata can be stripped by any tool that re-saves the image. A credential is proof of provenance when it is present; silence proves nothing either way.

C2PA (Coalition for Content Provenance and Authenticity) is the open standard behind "Content Credentials". A camera, editor or generative model signs a manifest into the file describing what made it and what was done to it. Because the manifest is cryptographically signed and bound to the file's bytes, both the claim and any subsequent tampering are detectable.

Those are two separate questions. The signature check asks whether the bytes were signed by whoever holds the key. The trust check asks whether that key belongs to anyone recognised — it chains the signer's certificate to the official C2PA trust list. A file signed with a test or self-issued certificate passes the first and fails the second, which is the correct and honest outcome rather than a bug.

No, and the standard is explicit about it: a CAWG identity assertion “should not be construed to convey either attribution or ownership”. What it does say is narrower and more useful — a named actor signed over this manifest's content with their own credential, in whatever role they declared. Where the credential comes from an identity aggregator, the names and accounts you see are that aggregator's word: it attests that the actor showed it those signals and showed it this asset, nothing more.

This page reports an actor as unproven unless you have given it a trust list of your own. That is the normal outcome, not a warning: nobody publishes a list of authorities that vouch for people, so a genuine signature by a real person still reads as unproven here.

The manifest records a hash of the file's own bytes at signing time. If that hash no longer matches, the content has changed since it was signed — a crop, a re-compression, or a deliberate edit. The credential still tells you truthfully who signed the original; it simply no longer describes the file you have.

Because the credential is real and nothing checked it against these bytes. It happens when the manifest describes something the file carries rather than the file itself — an image or a font inside a PDF, which is where the C2PA spec says such a manifest belongs — and when a fragmented video is inspected without its fragments. It is neither a pass nor a failure: the signature and the signer are exactly as reported, and the question “are these the signed bytes?” simply has no answer here. A green tick would claim more than the validator did.

No. The validator is compiled from Go to WebAssembly and runs inside this page, so your file is read by your own browser and never sent over the network. There is no server to upload to. The shareable link encodes the result in the URL, never the file.

Yes. The page creates a key in your browser's WebCrypto store as non-extractable, or imports one you already have, and the validator's Go code — compiled to WebAssembly — builds the manifest and asks the key for each signature. The key never leaves the browser; only the signed file does, as a download. A test identity made here is self-signed, so verifiers will report the signature as valid and the signer as untrusted — that is the honest outcome, not a fault. To be trusted, import a certificate chain issued by a CA on the C2PA trust list. Timestamping needs a timestamp authority that allows cross-origin requests, which most public ones do not.

JPEG, PNG, WebP, GIF, TIFF, DNG, HEIC, HEIF, AVIF, SVG, MP4, MOV, M4A, AVI, WAV, MP3 and PDF. If a format is not listed, the page will say so rather than silently reporting "no credentials".