Certificate Key Matcher
You can check with the SHA Checksum whether a certificate matches a private key, or a CSR matches a certificate on your own computer by using the OpenSSL commands below:
openssl pkey -in privateKey.key -pubout -outform pem | sha256sum
openssl x509 -in certificate.crt -pubkey -noout -outform pem | sha256sum
openssl req -in CSR.csr -pubkey -noout -outform pem | sha256sum