SNI stands for “Server Name Indication,” which is a technology used in the Transport Layer Security (TLS) protocol to allow multiple SSL/TLS certificates to be hosted on a single IP address.
In the past, a single IP address could only be associated with a single SSL/TLS certificate. This meant that if a website owner wanted to host multiple websites on a single server, each with its own SSL/TLS certificate, they would need to have a unique IP address for each certificate. This approach was not very scalable or cost-effective.
SNI technology solves this problem by allowing multiple SSL/TLS certificates to be hosted on a single IP address. When a client connects to a server using TLS, it sends the requested domain name as part of the handshake process. The server can then use this information to select the correct SSL/TLS certificate and complete the connection.
SNI is widely used on the internet today, and it has become the de facto standard for hosting multiple SSL/TLS certificates on a single IP address. It is supported by all major web browsers, including Google Chrome, Mozilla Firefox, and Microsoft Edge, as well as most modern web servers, such as Apache and Nginx.