This page must be opened over https://. Browsers only allow the camera and signature checks on secure pages.
Check a certificate
Scan the QR code printed on the certificate. You will see whether the college issued it and whether it is still valid.
Hold the QR code steady, filling most of the frame. Move closer if it doesn't read.
Paste the text a QR scanner app read from the certificate.
Compare these details with the printed certificate. They must match exactly.