not "automatically", no. You need to manually set the connection's IPVersion property to Id_IPv6 (unless you recompile Indy with IdIPv6 defined in IdCompilerDefines.inc, then IPVersion will default to Id_IPv6). In the case of TIdHTTP specifically, it obtains server info from a URL instead of set properties, so if you want to connect to an HTTP/S server using IPv6, you need to wrap the host portion of the URL in brackets. RFCs 2732 and 3986 require brackets around IPv6 IP addresses only, but TIdHTTP currently requires brackets around hostnames as well if you want it to perform an IPv6 DNS lookup. Indy is currently dependant on the IPVersion property being set and is not coded to resolve a hostname to both IPv4 and IPv6 at the same time and then attempt every address reported until a connection is successful. It lookups a hostname to either IPv4 or IPv6 only and then attempts a connection to the first IP reported only.