Fixing NET::ERR_CERT_COMMON_NAME_INVALID
The certificate doesn't cover the exact hostname the browser is loading.
50 guides decoding specific error codes and messages across browsers, developer tools, and platforms — with the fix, not just the explanation.
The certificate doesn't cover the exact hostname the browser is loading.
Either the certificate is expired, or the visitor's device clock is wrong.
The chain of trust is broken — usually a missing intermediate certificate.
An old certificate signed with SHA-1 or another deprecated algorithm.
The client and server share no compatible protocol version or cipher suite.
Often means plain HTTP is being served on the HTTPS port.
Firefox's version of the cipher/protocol mismatch error.
Almost always means plain HTTP is being served where HTTPS is expected.
Same underlying causes as desktop, with one Android-specific wrinkle worth checking.
iOS is particularly strict about certificate validity periods and algorithm requirements.