Adding an additional **SAN certificate** (*Subject Alternative Name*) with SSL Certificate purchase, can secure multiple domains on single server. If you want to secure two domains on single server, then you should buy a 1 certificate with adding a 1 SAN certificate during purchase. *Below table shows the number of domains on single server with requirement of SSL Certificates:* > 2 domains = 1 Certificate + 1 SAN > 3 domains = 1 certificate + 2 SANs > : : > : : > N domains = 1 Certificate + (n-1) SANs Generally, Major certificate Authorities allows you to add additional SAN up to 24. It may vary by Certificate Authority. ###Selection of Certificate:### There are three types of SSL Certificates **DV** (*domain validated*), **OV** (*organization validated*) and **EV** (*extended validation*) certificates. You should buy OV or EV certificate, because it has better SAN option then the DV certificates.