Is OIDC the Same as OAuth2? Do You Need OIDC for Login?

OAuth 2.0 and OpenID Connect (OIDC) are distinct yet complementary protocols often involved in user authentication and authorization for web and mobile applications. OAuth 2.0 is primarily an authorization framework that allows third-party applications to access user data without exposing passwords, but it does not authenticate users or provide identity information. OIDC, built on top of OAuth 2.0, adds an identity layer that enables authentication, allowing applications to verify users' identities, retrieve profile information, and establish secure sessions through ID tokens. While OAuth 2.0 is suitable for accessing APIs and delegating permissions, OIDC is essential for login functionalities, identity verification, and session management, making it crucial for applications that require user authentication and personalized experiences. Using OAuth 2.0 for login is insecure without OIDC, as access tokens lack identity claims and are prone to security risks. OIDC is particularly advantageous for implementing single sign-on (SSO) across multiple services, integrating with enterprise identity providers, and building secure, scalable authentication flows in modern applications such as single-page applications (SPAs), mobile apps, and business-to-business (B2B) platforms.