Server Name Indication (SNI) is a recent extension of the TLS/SSL protocol that was developed to compensate for the depletion of IPv4 addresses. SNI allows a browser to indicate at the beginning of a secure session which domain name it is trying to connect with, so that the web server can select and present the correct certificate to the browser.

The great advantage of SNI is that multiple SSL certificates can now be linked to a single IP address, and it is no longer necessary to sacrifice one IP address per SSL website.