v1.2 and TLSv1.3 are all available by default in a standard build of OpenSSL. However special run-time configuration is required in order to make TLSv1.0 and TLSv1.1 work successfully.</p>

<p>OpenSSL will always try to negotiate the highest protocol version that it has been configured to support. In most cases this will mean either TLSv1.3 or TLSv1.2 is chosen.</p>

<h1 id="CERTIFICATES">CERTIFICATES</h1>

<p>In order for a client to establish a connection to a server it must authenticate the identify of t