---
title: SP-initiated SSO
sidebar_custom_props:
    termName: SP-initiated SSO
    tags:
        - SAML
    shortDescription: SSO flow started at the Service Provider.
    longDescription: User starts at the SP, which sends an AuthnRequest (often via Redirect) to the IdP. After authentication, the IdP posts the Response to the SP's ACS, optionally preserving RelayState.
---
