I am integrating an ASP.MVC site with Salesforce. The front end is an existing ASP site with iframes in some places that lead to Salesforce. ASP side is also the Identity Provider. I have set up Salesforce Identity Provider and it appears in the login page where I select my identity provider and if there's a session in ASP side it automatically logs into Salesforce also. My problem is that I don't want the user to see the Salesforce login page and click my identity provider. I need some way to tell Salesforce to automatically use my identity provider when there is a guest access.
Using Salesforce Communities:
Edit the Community's Login Page, and ensure that your SAML IdP is the only selected login option:
Now users will be automatically directed to the IdP for login, instead of seeing the Salesforce Community login page.
For Internal Users
You need to create a My Domain (see documentation). My Domain gives your org a custom login URL, for example,
Once you have My Domain, configure the Login Page Branding so the SAML IdP is the only selected Authentication Service:
Now users will be automatically directed to the IdP for login, instead of seeing the Salesforce login page.