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cheatsheet-tldr/tldr/openssl-s_client
2025-12-20 00:20:53 +00:00

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---
syntax: markdown
tags: [tldr, common]
source: https://github.com/tldr-pages/tldr.git
---
# 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`