Find out what a server is actually running and which protocols it will negotiate - useful before you buy a certificate for it, and useful when one will not install.

A host name or an IP address.
Working

Why it matters

  • Installation steps differ by server - Apache, nginx, IIS and cPanel each want the files in a different shape
  • An old TLS version tells you the platform itself is out of support
  • Knowing the software up front is the difference between a five-minute install and an afternoon

Before you order

Certificate files come in different formats and the right one depends on what you run. Windows and IIS expect a PFX bundle; Apache and nginx want separate PEM files and an explicit chain file; Java servers want a keystore. Knowing what answers on port 443 tells you which set to ask for.

When an install will not take

If a certificate is installed but the site still warns, the problem is usually the server rather than the certificate: an old build that cannot send a full chain, a second virtual host answering first, or a proxy in front terminating TLS with its own certificate. Identifying the software is the first step to telling those apart.