User authentication is essential for modern applications, serving as the entry point to secure access and protect sensitive data, while also enhancing user experience and aiding compliance. It is crucial for both consumer apps and enterprise SaaS platforms. The blog focuses on external user authentication, highlighting various solutions like Descope, Microsoft Entra External ID, Okta Customer Identity Cloud, OneLogin, Amazon Cognito, Firebase Authentication, Keycloak, and Supabase Auth, each with unique capabilities and ideal applications. Descope stands out for its customizable, no-code authentication flows and multi-tenant support, making it suitable for both startups and scaling organizations. Meanwhile, other providers like Keycloak offer self-hosting flexibility, and Microsoft Entra External ID excels in enterprise governance, showcasing the diverse options available depending on an organization's specific needs, stack, and growth objectives.