IDP initiated SSO start it's SSO journey from IDP side. When we say "SP-initiated", we go to SP's site and click on some link which forwards us to the IDP for authentication. IDP initiated SSO is called with some custom url ( i.e: `https://my_idp_hostname/idp/profile/SAML2/Unsolicited/SSO?providerId=https://sp.com/SAMLRedirector/ClientSAMLLogin.aspx` ) and it will take user to SP (one time) after IDP authentication. For IDP initiated SSO, most configurations are configured from IDP side ( sometimes, it's required to write metadata for SP ). We need to know "where" to point the IDP to redirect the user. IDP initiated SSO requires producing highly customized metadata for each target application. We recommend reaching out to a [Gluu integration partner](http://gluu.org/current-partners) for support on IDP initiated SSO.