Server Name Indication (SNI)


Server_Name_Indication is an extension to the TLS computer networking protocol by which a client indicates which hostname it is attempting to connect to at the start of the handshaking process.

SNI is more and more a requirement (all of Cloudflare FreeSSL works only with SNI)


with Openssl

openssl s_client \
  -servername # sni settings


SNI is supported by all modern browsers, but outside of this it is not supported with older versions of:

  • Java (up to JDK6),
  • python (up to 2.7.9),
  • with some commonly used libraries on Android etc.

Documentation / Reference

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