SSL, TLS and HTTPS
TLS protects data in transit and, for HTTPS, verifies the contacted server's identity through its certificate. SSL is the obsolete predecessor, although the term SSL certificate remains common. HTTPS does not establish that content is trustworthy. Fraudulent websites can also hold valid certificates.
Certificates and connections
A certificate contains public keys, names and validity dates, among other information. The client checks its trust chain, hostname match and lifetime. The handshake establishes session keys for encryption. The private key must remain secret. TLS 1.2 and 1.3 are commonly used; SSL and TLS 1.0/1.1 are obsolete.
DV, OV, EV and wildcards
DV verifies domain control; OV and EV additionally validate organization information. They do not guarantee safe content or automatically provide stronger encryption. SAN entries can cover several names. *.example.com covers www.example.com, but neither example.com itself nor a.b.example.com.
Checking and renewal
Certificates must be renewed before expiry; their lifetime depends on issuer and profile. Our SSL checker tests trust chain, hostname and validity from the server. It is not a complete protocol, cipher or revocation scan. Browser warnings should be resolved by fixing the underlying cause.