Single sign-on (SSO) is a critical tool for providing seamless digital access by allowing users to authenticate once and gain access to multiple applications, thereby reducing password fatigue and enhancing security. The text focuses on customer SSO, which is designed to securely connect external users such as clients and partners, while maintaining a branded experience. It outlines how customer SSO uses protocols like SAML, OpenID Connect (OIDC), and OAuth 2.0 to establish trust between applications and identity providers. The text also highlights the benefits of customer SSO, such as simplifying onboarding, lowering support costs, and providing tenant-specific access without extensive custom integrations. Several leading customer SSO providers are discussed, including Descope, Auth0, Amazon Cognito, Microsoft Entra, Firebase Authentication, OneLogin, and Keycloak, each offering unique features and capabilities. The text concludes by emphasizing the competitive advantage of modern customer SSO solutions when implemented thoughtfully, with Descope noted for its tenant-aware architecture and comprehensive suite of tools that facilitate secure and consistent login experiences.