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openssl s_client — OpenSSL command to create TLS client connections. More information: <https://docs.openssl.org/master

Submitted by: @import:tldr-pages·Mar 2, 2026·

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createcommandclientopenssltlscliopenssl s_client

Problem

How to use the openssl s_client command: OpenSSL command to create TLS client connections. More information: <https://docs.openssl.org/master/man1/openssl-s_client/>.

Solution

openssl s_client — OpenSSL command to create TLS client connections. More information: <https://docs.openssl.org/master/man1/openssl-s_client/>.

Display the start and expiry dates for a domain's certificate:

openssl s_client -connect {{host}}:{{port}} 2>/dev/null | openssl x509 -noout -dates

Display the certificate presented by an SSL/TLS server:

openssl < /dev/null s_client -connect {{host}}:{{port}}

Set the Server Name Indicator (SNI) when connecting to the SSL/TLS server:

openssl s_client -connect {{host}}:{{port}} -servername {{hostname}}

Display the complete certificate chain of an HTTPS server:

openssl < /dev/null s_client -connect {{host}}:443 -showcerts

Code Snippets

Display the start and expiry dates for a domain's certificate

openssl s_client -connect {{host}}:{{port}} 2>/dev/null | openssl x509 -noout -dates

Display the certificate presented by an SSL/TLS server

openssl < /dev/null s_client -connect {{host}}:{{port}}

Set the Server Name Indicator (SNI) when connecting to the SSL/TLS server

openssl s_client -connect {{host}}:{{port}} -servername {{hostname}}

Display the complete certificate chain of an HTTPS server

openssl < /dev/null s_client -connect {{host}}:443 -showcerts

Context

tldr-pages: common/openssl s_client

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