Microsoft Entra External ID and Azure AD B2C are two separate platforms powered by Evolved Security Token Service (ESTS) and Identity Experience Framework (IEF) respectively. Entra External ID is our new converged platform which is future proof and developer friendly to meet all your identity needs – B2E, B2B and B2C. At the same time, we will still continue to support Azure AD B2C as a separate product offering with no change in SLA, and we’ll continue investments in the product to ensure security, availability, and reliability.
For more questions visit Microsoft Entra External ID for customers FAQs.