The main differences between System Assigned Managed Identities and User Assigned Managed Identities in Azure are as follows:
- Creation and Lifecycle: System Assigned Managed Identities are automatically created when an Azure resource (like a virtual machine or app service) is set up. They share the same lifecycle as the parent resource; if the resource is deleted, the managed identity is also deleted. In contrast, User Assigned Managed Identities are created as standalone Azure resources and have an independent lifecycle, requiring explicit deletion[3][4].
- Scope and Sharing: System Assigned Managed Identities are tied to a single Azure resource and cannot be shared across multiple resources. User Assigned Managed Identities, however, can be shared across multiple resources, allowing for a uniform permission set across different services[2][3].
- Use Cases: System Assigned Managed Identities are ideal for workloads contained within a single resource or when independent identities are needed. User Assigned Managed Identities are better suited for scenarios where multiple resources need to share the same identity, such as applications with multiple components requiring consistent access permissions[3][4].
- Management and Maintenance: Both types automatically handle credential rotation and secure delivery, but User Assigned Managed Identities offer more flexibility in managing identities across different resources, which can be beneficial in complex environments[3][7].
Citations:
[1] https://www.atmosera.com/blog/azure-service-principal-vs-managed-identity/
[2] https://www.reddit.com/r/AZURE/comments/xkzxrc/azure_managed_identity_vs_user_assigned_managed/
[3] https://learn.microsoft.com/en-us/entra/identity/managed-identities-azure-resources/overview
[4] https://docs.azure.cn/en-us/entra/identity/managed-identities-azure-resources/overview
[5] https://stackoverflow.com/questions/61322079/difference-between-service-principal-and-managed-identities-in-azure
[6] https://www.youtube.com/watch?v=tFzIjBIlWUw
[7] https://learn.microsoft.com/en-us/entra/identity/managed-identities-azure-resources/managed-identity-best-practice-recommendations
[8] https://blog.johnfolberth.com/azure-managed-identities-user-vs-system-assigned/