What does SNI mean?

SNI, Server Name Indication, is an extension of the TLS protocol. It indicates which hostname the browser is contacting at the beginning of the "handshake" process; allows a server to securely host multiple SSL certificates for multiple sites that exist on the same IP address.

When using SNI, the server's hostname is included in the TLS handshake, which allows HTTPS websites to have unique TLS certificates, even if they are on a shared IP address.

How does SNI work?

SNI allows a web server to host multiple sites on a single IP address via extensions of the SSL or TLS handshake. This extension enables the client to specify the requested domain in the initial TLS request, allowing the server to select an appropriate SSL certificate to send back to the client for verification.

SNI Support (Browser and Tools)

As with all the latest technology, SNI’s browsing Server and server adoption is not yet widespread. An estimated 15% of browsers currently do not have SNI support, and those legacy browsers will see the website's default certificate and a possible mismatch between the certificate hostname and the website name.

Today's most popular web browsers and modern operating systems support SNI; unsupported browsers will receive a default certificate and will typically issue a certificate warning. The following lists some supported browsers:

1. Default browser for Android phones - starting with 4.x

2. Default browser for Android tablets - starting with 3.x

3. BlackBerry 10 Web Browser

4. Google Chrome - starting from version 6.0

5. Internet Explorer - starting from version 7 (Windows XP does not support SNI)

6. Mozilla Firefox - starting from version 2.0

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