BuiltWith supports SAML SSO single sign on. We can enable this at no extra cost for Team users of BuiltWith Pro.
Entity Id: https://pro.builtwith.com
ACS URL: https://pro.builtwith.com/samsam/Acs
Start URL: https://pro.builtwith.com
Binding Type: HTTP Redirect
Name ID Format: urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress