Single sign-on (SSO) is a modern authentication method that allows users to sign in with services like Google and Apple, providing developers with tokens to verify identities and access user data. Clerk simplifies implementing SSO by managing token lifecycles and offering easy-to-use functions to retrieve access tokens, enabling developers to focus on application features rather than authentication infrastructure. The article highlights how Clerk's capabilities are demonstrated through the BookMate demo, an open-source application that integrates Google Calendar data to avoid scheduling conflicts. By using Clerk, developers can securely access third-party services with minimal code and maintain seamless user experiences, making it an ideal solution for applications requiring SSO integration.