Front-Channel vs Back-Channel Logout in OpenID Connect (OIDC)

In modern authentication systems built on OpenID Connect (OIDC), we implement Single Sign-On (SSO) correctly, but we do not focus enough on the logout part. However, managing sessions across relying parties is just as important as the login itself. Logout is not just about ending a session in one application — it is about complete session termination across all relying parties (RPs). OIDC provides two standardized logout implementation mechanisms: Front-Channel Logout (OpenID Connect Front-Channel Logout 1.0) Back-Channel Logout (OpenID Connect Back-Channel Logout 1.0) Both are official specifications designed to solve the single logout problem, and understanding the differences between them is critical for building a secure SSO system. (1) Front-Channel Logout Front-Channel Logout is defined in the OpenID Connect Front-Channel Logout 1.0 specification. It is a browser-based logout mechanism. How it works: User or RP initiates logout RP redirects the user to the IdP’s end_session_endpo