System Assigned vs User Assigned Identity in Azure: Key Differences and Usage

In Azure, a system assigned identity is tied directly to a single resource and is created and deleted with it, while a user assigned identity is a standalone resource that can be shared across multiple resources. System assigned identities simplify management for single resources, whereas user assigned identities offer flexibility and reuse.

Quick Comparison

This table summarizes the main differences between system assigned and user assigned identities in Azure.

Feature	System Assigned Identity	User Assigned Identity
Creation	Automatically created with the resource	Manually created as a separate resource
Scope	Bound to one Azure resource	Can be assigned to multiple resources
Lifecycle	Deleted when the resource is deleted	Independent lifecycle, persists after resource deletion
Use Case	Simple scenarios with single resource	Shared identity across multiple resources
Management	Less management overhead	Requires explicit management
Resource ID	Resource-specific ID	Unique resource ID usable by many

Key Differences

A system assigned identity is created and enabled directly on an Azure resource like a Virtual Machine or App Service. It is tightly coupled to that resource, meaning when the resource is deleted, the identity is also removed automatically. This makes it easy to manage but limits its use to that single resource.

On the other hand, a user assigned identity is created as a separate Azure resource. It can be assigned to one or more Azure resources, allowing multiple services to share the same identity. This identity remains even if the resources using it are deleted, giving you more control over its lifecycle.

System assigned identities are best for simple, one-to-one identity needs, while user assigned identities are ideal when you want to reuse the same identity across multiple resources or manage identity lifecycle independently.

Code Comparison

Here is how you enable a system assigned identity on an Azure Virtual Machine using Azure CLI.

bash

az vm identity assign --resource-group MyResourceGroup --name MyVM

Output

{
  "principalId": "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx",
  "tenantId": "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx",
  "type": "SystemAssigned"
}

User Assigned Identity Equivalent

Here is how you create a user assigned identity and assign it to a Virtual Machine using Azure CLI.

bash

az identity create --resource-group MyResourceGroup --name MyUserAssignedIdentity
az vm identity assign --resource-group MyResourceGroup --name MyVM --identities /subscriptions/{subscriptionId}/resourceGroups/MyResourceGroup/providers/Microsoft.ManagedIdentity/userAssignedIdentities/MyUserAssignedIdentity

Output

{
  "clientId": "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx",
  "principalId": "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx",
  "tenantId": "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx",
  "type": "UserAssigned"
}

When to Use Which

Choose system assigned identity when you have a single Azure resource that needs an identity and you want simple automatic lifecycle management without extra setup.

Choose user assigned identity when you want to share the same identity across multiple resources, need to manage the identity lifecycle separately, or require more control over permissions and auditing.

Key Takeaways

System assigned identities are tied to one resource and deleted with it.

User assigned identities are standalone and can be shared across resources.

Use system assigned for simple, single-resource scenarios.

Use user assigned for shared identity and independent lifecycle needs.

Azure CLI commands differ for creating and assigning each identity type.