Free verifier
Verify a photo or video.
Paste a CaptureSeal verify link, or drop a .seal Proof File. Your browser checks the signature and fingerprints the files itself. Your files never leave this device.
or
Files never leave this deviceWebCrypto + hash-wasmOr verify offline with OpenSSL
No CaptureSeal file to hand? Download the demo Proof File (.seal) and drop it above, or open the demo record.
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Questions
About the verifier
Does a verify link prove the photo I was sent is genuine?
No. A link alone doesn’t prove the photo; the check does. A link shows that a signed record exists and what the capturing phone recorded. Drop the exact file you received and it’s compared bit for bit: only an identical file is genuine.
Is my file uploaded?
No. Your browser calculates the file’s SHA-256 fingerprint itself and compares it with the record. The file never leaves your device. Only a pasted verify link makes a request, to fetch that public record.
What can I check here?
A CaptureSeal verify link (from a QR code or a message), or a Proof File: the single .seal file CaptureSeal’s Share → Proof File makes. You can also drop the separate manifest.json, manifest.sig and photo or video files together.
What is a .seal file?
CaptureSeal’s Proof File: one file anyone can verify. Inside it’s a standard, uncompressed zip archive holding the stamped photo or video, the signed record (manifest.json), its signature (manifest.sig) and a README, so it stays inspectable with ordinary tools for as long as zip exists. Its first entry, captureseal, names the format. On iPhone it opens in CaptureSeal with a preview right in Files, Mail and Messages; on any computer, drop it here. A copy renamed to .zip works too.
Why doesn’t my copy match?
The file isn’t byte-for-byte the one that was sealed. It may have been edited, cropped or filtered, or simply re-saved or compressed. Messaging apps like WhatsApp recompress media, so forwarded copies never match. Ask for the original file or the Proof File.
Does it work with large videos?
Yes. Files are fingerprinted in 8 MB chunks, so videos of a gigabyte or more work in current Safari, Chrome and Firefox.
Can I check a photo that wasn’t taken with CaptureSeal?
This verifier only checks CaptureSeal records. For other photos, see how to tell if a photo is edited.