Migrating authentication systems requires careful planning and consideration, involving two main steps: migrating user login data and updating application code. The complexity of this process depends on the existing authentication setup, such as whether user IDs need to be retained or if user login methods, such as passwords or social logins, need to be altered. Password migrations can be challenging, particularly when existing password hashes cannot be exported, as seen with providers like AWS Cognito and Auth0. Additionally, the process may involve transferring authorization data, depending on whether the current or new provider handles authorization. Various migration strategies exist, from a complete switch to maintaining dual systems temporarily or segmenting users to use different authentication methods. Each approach has its complexities, and careful planning is essential to ensure a smooth transition while maintaining user experience and security.