Integrating Azure AD B2C authentication in a React application using the msal-react library offers a streamlined approach to managing user authentication without building a system from scratch. Azure AD B2C, a Microsoft service, provides a scalable and secure solution that supports various authentication methods, including email-based and social logins. The msal-react library facilitates this integration by using React components like MsalProvider, AuthenticatedTemplate, and UnauthenticatedTemplate, and hooks like useIsAuthenticated and useMsal to manage authentication flows and user state. The setup process involves configuring the msal-react library with a client ID and authority, then wrapping the app within an MsalProvider component to enable authentication. Developers can choose between popup or redirect methods for user login, with redirect being preferred due to its compatibility and reliability. Additionally, the library's hooks allow developers to manage user authentication states dynamically within the app, providing a robust solution for securing frontend applications.