The SSLFOR Key Matcher compares the RSA public modulus and exponent derived from a certificate or CSR with the corresponding values derived from a private key. If both components match, the materials belong to the same RSA key pair.
This check is useful when several private-key files exist on a server, after migrating certificates between systems, or when an issued certificate cannot be installed because the original key is uncertain.
The comparison is performed in the browser. The private key is not sent to the SSLFOR backend.