Integrity check
COA file checker
A key lookup tells you a record exists. This tells you whether the PDF in your hand is the one we actually issued — down to the byte.
Drop the certificate PDF here
The file is hashed in your browser. It is never uploaded to us.
How it works
When we issue a certificate we record a SHA-256 fingerprint of the exact PDF. Your browser computes the same fingerprint from your copy and sends us only those 64 characters. If they match, the documents are identical; if a single pixel of a single digit changed, they won’t.
Because only the fingerprint is transmitted, we never see the file — which matters if the report contains a client name you’d rather not share.
Catches edited numbers
The classic forgery is a real certificate with the purity figure raised a point or two. The key still verifies. The hash does not.
Catches recycled certificates
A certificate from a good batch attached to a different batch keeps its original sample and batch fields — compare them against what you were sold.
What it can't do
It can't tell an edited file from one we never issued; both come back as no match. And a legitimate certificate re-saved by a PDF viewer will also miss — ask the sender for the original.