Azure Managed Identity vs Service Principal: Which to Use

• Last updated: 10 September 2026
• Azure
• Written by Editorial Team

Most Azure authentication mistakes trace back to one habit: an application with a client secret sitting in a configuration file, a key vault, or worse, a repository. Someone will eventually have to rotate that secret, and someone will eventually forget to. Azure gives you two Microsoft Entra ID identity types built to solve exactly this problem: managed identity and service principal. Nearly every piece of content comparing them treats the two as separate, competing options. That framing is the first thing worth correcting.

This guide explains what each identity type actually is, how they’re related under the hood (not just how they differ), when to use which one, how to create both through the CLI and as code, how to migrate an application off a service principal secret, and the mistakes that turn a good identity strategy into a support ticket.

The Fact Most Comparisons Skip: A Managed Identity Is a Service Principal

Here is the detail that reframes everything else in this article: a managed identity is not an alternative to a service principal. It is a service principal, specifically, a special type that Azure creates and manages automatically in Microsoft Entra ID on your behalf. When you enable a managed identity on an Azure resource, Azure creates a service principal of a special type behind the scenes. You never see the credential, never rotate it, and never store it, but structurally, what’s authenticating to your other Azure resources is still a service principal.

Once that clicks, the real comparison stops being “which of these two things should I pick” and becomes “should Azure manage this service principal’s credentials for me, or do I need to manage them myself.” That second framing is also, almost word for word, Microsoft’s own guidance: use a managed identity if possible, and a service principal if not. Everything below exists to help you figure out which side of that line your specific workload falls on.

What Is Azure Managed Identity?

A managed identity is an identity assigned to an Azure resource where Azure creates, rotates, and secures the underlying credentials automatically. Instead of an application storing a password or secret to authenticate, it uses its managed identity, and Azure handles everything behind that identity.

A typical flow looks like this: an Azure App Service needs to read from Azure Storage. Rather than embedding a storage account key inside the application, the App Service is assigned a managed identity, and that identity is granted permission to the storage account. No password is ever created, stored, or rotated by a human.

System-Assigned Managed Identity

Created directly on an Azure resource and tied to that resource’s lifecycle. Delete the resource, and Azure automatically deletes the identity with it. Only that specific resource can use the identity to request tokens, which makes it a clean one-to-one fit for a single application with no need to share credentials elsewhere. Role-based access control (RBAC) is used to grant it permissions, the same as any other identity.

User-Assigned Managed Identity

Created as a standalone Azure resource, independent of anything it’s attached to. It can be assigned to multiple resources simultaneously, and it persists even if every resource using it is deleted, requiring its own explicit deletion. This is the recommended pattern when several resources, say, a set of Azure Functions that all need the same downstream permissions, should share one identity rather than each getting its own.

What Is a Service Principal?

A service principal is the identity in Microsoft Entra ID that represents a non-human entity, an application, workload, tool, or automation, so it can authenticate and access Azure resources. It’s created in each tenant where the application is used and references a globally unique application object. Unlike a managed identity, its lifecycle is not tied to any specific Azure resource: you create it, assign it permissions, and configure the application to authenticate with it.

That configuration is also where the real work lives. A traditional service principal authenticates using either a client secret or a certificate, and Microsoft’s own guidance is direct about which is preferable: use client certificates over client secrets where possible, since certificates are harder to leak accidentally and support stronger validation. Either way, your team owns creating it, storing it securely, rotating it before it expires, and revoking it when it’s no longer needed. That ownership is the entire trade-off against a managed identity, spelled out plainly.

Managed Identity vs Service Principal: Full Comparison

Factor	System-Assigned MI	User-Assigned MI	Service Principal
Created	Automatically, on the resource	As a standalone resource	Manually, via app registration
Lifecycle	Tied to the resource	Independent, needs manual deletion	Independent, needs manual deletion
Can be shared	No, one resource only	Yes, across many resources	Yes, across many resources
Credential management	Automatic, by Azure	Automatic, by Azure	Manual, by your team
Works outside Azure	No	No	Yes
Best for	A single Azure-hosted app or service	Multiple resources sharing one identity	External apps, multi-cloud, hybrid, CI/CD

When to Use Managed Identity

Managed identity is the right first choice whenever a workload runs on Azure and needs to reach another Azure service. Consider it when:

• Your application or service runs on Azure infrastructure that supports managed identity (App Service, Functions, VMs, AKS, Container Apps, and most other compute services do)
• You want to eliminate secret management for this connection entirely, not just make it more convenient
• The target resource supports Microsoft Entra authentication (Key Vault, Storage, Azure SQL, and most first-party Azure services do)
• You’re connecting one Azure service to another, the single most common authentication pattern in any Azure environment

A concrete example: an Azure Function needs to read secrets from Azure Key Vault. Instead of storing a Key Vault access key in the function’s application settings, you assign the function a managed identity and grant that identity permission on the vault. No secret is ever created for this connection, which also means there’s nothing to leak, rotate, or forget about.

A Common Trip-Up: Key Vault RBAC vs Access Policies

This specific pairing, a managed identity reading from Key Vault, is also where a lot of first attempts stall out, for a reason that has nothing to do with the identity itself. Azure Key Vault supports two separate, mutually exclusive permission models: the legacy vault access policy model, and the Azure RBAC permission model, which Microsoft now sets as the default for newly created vaults. A managed identity granted a role like Key Vault Secrets User only gets access if the vault is actually configured to use the Azure RBAC model; if the vault is still running on the legacy access policy model, that role assignment does nothing, and the identity needs an access policy entry instead. Checking which permission model a given vault uses, visible under its access configuration settings, before troubleshooting why a role assignment that looks correct isn’t granting access, saves a genuinely common half hour of confusion.

When to Use a Service Principal

A service principal earns its place when a managed identity genuinely isn’t an option, which comes down to one core fact: managed identities cannot be used for services hosted outside Azure. Reach for a service principal when:

• Your workload runs outside Azure entirely, on-premises, in another cloud, or in a CI/CD runner that isn’t itself an Azure resource
• You’re building a script or tool that calls Azure APIs or SDKs from somewhere that can’t hold a managed identity
• The application needs to authenticate across multiple tenants, which service principals support and managed identities do not
• You’re integrating a third-party or multi-cloud automation platform that expects a standard OAuth client credential flow

The good news: even here, you don’t have to default to a stored secret. That’s what workload identity federation is for.

Workload Identity Federation: Service Principal Access Without a Stored Secret

This is the detail most comparisons of this topic skip entirely, and it matters because it closes the biggest practical gap between the two identity types. Workload identity federation lets a service principal authenticate using a trust relationship instead of a client secret or certificate. An external identity provider issues a short-lived token, Entra ID validates it against a configured federation, and the service principal receives an Azure access token, with no long-lived credential stored anywhere.

The most common real-world example is a CI/CD pipeline. A GitHub Actions workflow or an Azure DevOps pipeline can authenticate to Azure using workload identity federation: Entra ID trusts tokens issued by GitHub’s or Azure DevOps’s own OIDC provider for that specific repository and workflow, so the pipeline gets Azure access without a client secret sitting in a repository secret store waiting to be leaked in a misconfigured log line. If your team is currently storing a service principal secret in a CI/CD platform’s secret manager purely to let a pipeline deploy to Azure, that’s very likely the first candidate for this migration.

The Same Pattern Inside Kubernetes: AKS Workload Identity

Azure Kubernetes Service uses this same federation mechanism to solve a related problem: how a pod running inside a cluster authenticates to Azure without every pod on a node sharing one identity, and without a client secret stored in a Kubernetes manifest or Helm values file. Microsoft Entra Workload ID binds a user-assigned managed identity to a specific Kubernetes service account through a federated identity credential, matched against the cluster’s OIDC issuer and that service account’s subject. Once configured, a pod using that service account can request Azure tokens directly, no secret ever touches the cluster, and revoking one workload’s access means removing one federated credential rather than hunting down where a shared secret might have been copied. It’s the same underlying idea as the CI/CD example above, a trust relationship instead of a stored credential, applied one layer down at the pod level.

Creating Managed Identities and Service Principals with Code

The portal works for a one-off resource, but production environments should create identities as code, the same discipline that applies to a well-structured Azure management group hierarchy or landing zone.

Azure CLI

# Enable a system-assigned managed identity on an existing App Service
az webapp identity assign --name my-app --resource-group my-rg

# Create a standalone user-assigned managed identity
az identity create --name my-shared-identity --resource-group my-rg

# Create a service principal for external / CI use
az ad sp create-for-rbac --name my-external-app --role Contributor --scopes /subscriptions/<sub-id>

Azure PowerShell

# Enable a system-assigned managed identity
Set-AzWebApp -ResourceGroupName my-rg -Name my-app -AssignIdentity $true

# Create a user-assigned managed identity
New-AzUserAssignedIdentity -ResourceGroupName my-rg -Name my-shared-identity

# Create a service principal
New-AzADServicePrincipal -DisplayName my-external-app

Bicep

resource appService 'Microsoft.Web/sites@2023-12-01' = {
  name: 'my-app'
  location: resourceGroup().location
  identity: {
    type: 'SystemAssigned'
  }
}

resource userAssignedIdentity 'Microsoft.ManagedIdentity/userAssignedIdentities@2023-01-31' = {
  name: 'my-shared-identity'
  location: resourceGroup().location
}

Defining identities alongside the resources that use them, in the same template, keeps permissions auditable and reviewable in source control rather than scattered across portal clicks nobody remembers making.

Migrating from a Service Principal to a Managed Identity

The most common real-world project this topic leads to isn’t picking an identity type for something new, it’s replacing a service principal secret an existing Azure-hosted application has been using all along. The migration follows a predictable sequence:

• 1. Enable the managed identity

  Turn on a system-assigned or user-assigned managed identity on the Azure resource hosting the application, without touching the existing service principal yet.

• 2. Grant it identical permissions

  Assign the managed identity the same RBAC roles the service principal currently holds on every target resource. Run both identities in parallel during this step.

• 3. Update the application’s authentication code

  Switch the application to request tokens using the managed identity (via a library such as Azure Identity SDK’s DefaultAzureCredential or ManagedIdentityCredential) instead of the service principal’s client ID and secret.

• 4. Test thoroughly, then remove the old credential

  Confirm the application authenticates successfully end to end using only the managed identity. Only then revoke the service principal’s client secret or certificate, and if the service principal has no other purpose, delete it.

• 5. Remove the secret from wherever it was stored

  Clean up the now-unused secret from application configuration, Key Vault, or a CI/CD secret store. A revoked secret still sitting in a config file is a loose end, not a finished migration.

Which Option Is More Secure?

The honest answer is that either can be secure or insecure, since security depends on configuration and governance, not just which identity type you picked. That said, the structural advantage of managed identity is real: you cannot leak a credential you never created, store, or transmit. Azure handles the entire lifecycle, which removes an entire category of mistake from the table.

Service principals can absolutely be run securely, but the responsibility sits with your team: certificates over secrets where possible, workload identity federation over both wherever it’s supported, short expiration windows, and a real rotation procedure that survives a team member leaving. Poorly managed service principal credentials are a recurring theme in real-world Azure security incidents, not because the technology is weak, but because manual credential hygiene is where discipline slips. The right question for any identity decision isn’t “which type is inherently more secure,” it’s “which approach gives this specific application the access it needs with the least credential management risk,” and for anything running inside Azure, that answer is very often managed identity.

Common Identity Mistakes to Avoid

• Defaulting to a service principal out of habit. Teams that learned Azure identity before managed identity matured sometimes reach for a service principal even for workloads running entirely inside Azure, recreating credential management work that doesn’t need to exist.
• Granting broad roles instead of scoped ones. Assigning Contributor or Owner at a subscription scope because it’s faster than figuring out the specific role needed turns a single compromised identity into a much bigger incident than it needed to be.
• Creating a new system-assigned identity per resource when a shared user-assigned identity was the better fit. This scatters permissions across dozens of near-identical identities that are individually harder to audit than one well-scoped, shared one.
• Letting service principal secrets run without an expiration or rotation plan. A secret with no set expiration, or one nobody has a process to rotate, is a slow-motion incident waiting for the day it’s finally needed and found to be stale, revoked, or worse, still valid and long forgotten.
• Never revisiting old service principals after a migration. Applications get moved to managed identity, but the original service principal is left active “just in case,” quietly expanding the attack surface for no ongoing benefit.

How Apps4Rent Helps with Azure Identity and Access Management

Apps4Rent is a Microsoft Solutions Partner and Tier-1 Cloud Solution Provider, SOC 2 Type II certified, serving over 10,000 businesses since 2003. Choosing between managed identity and service principal is one piece of a much larger identity and access management picture, and it’s exactly the kind of decision that’s cheap to get right early and expensive to unwind later.

Our Azure consulting services include auditing how your applications currently authenticate, identifying every stored secret that could become a managed identity instead, designing least-privilege RBAC assignments, and building identity into your Azure landing zone from the start rather than retrofitting it. Once your environment is running, our Azure managed services keep identity configurations, access reviews, and credential hygiene current as your environment grows, so decisions made correctly today don’t quietly drift out of compliance a year from now.

Frequently Asked Questions

1. Is a managed identity a type of service principal?

   Yes. A managed identity is a special type of service principal that Azure creates and manages automatically in Microsoft Entra ID. Enabling a managed identity on a resource creates this special service principal behind the scenes, so the underlying identity model is the same; what differs is that Azure handles the credential lifecycle for you instead of your team managing it manually.

2. Is Azure managed identity better than a service principal?

   For Azure-hosted workloads that support it, managed identity is generally the better choice because Azure creates, rotates, and secures the credentials automatically, removing an entire category of manual credential risk. Service principals remain necessary for workloads hosted outside Azure, multi-tenant scenarios, and situations where managed identity isn’t supported. Microsoft’s own guidance is to use a managed identity if possible, and a service principal if not.

3. What is the difference between system-assigned and user-assigned managed identity?

   A system-assigned managed identity is created automatically on a specific Azure resource and shares that resource’s lifecycle, so it’s deleted automatically when the resource is deleted, and it can only be used by that one resource. A user-assigned managed identity is created as a standalone Azure resource, can be assigned to multiple resources at once, and persists independently until it’s explicitly deleted, making it the better fit when several resources need to share the same identity and permissions.

4. Can managed identity be used outside Azure?

   No. Managed identities are only available for services hosted in Azure. For workloads running on-premises, in another cloud, or anywhere outside Azure, Microsoft recommends using a service principal instead, ideally authenticated through workload identity federation rather than a stored client secret where the platform supports it.

5. Does a service principal always need a client secret?

   No. While client secrets and certificates are the traditional authentication methods for a service principal, many workloads can instead use workload identity federation, which lets an external identity provider such as GitHub Actions or Azure DevOps issue short-lived tokens that Entra ID trusts, eliminating the need to store a long-lived secret at all.

6. How do I migrate an application from a service principal to a managed identity?

   Enable a managed identity on the Azure resource hosting the application, grant it the same RBAC permissions the service principal currently has, update the application’s authentication code to request tokens through the managed identity, test the connection thoroughly, and only then revoke the service principal’s credential and remove it from wherever it was stored. Running both identities in parallel during testing avoids an authentication outage mid-migration.

7. What happens if a service principal’s secret expires?

   Any application relying on that client secret will fail to authenticate and lose access to the Azure resources it depends on until the secret is renewed or replaced. Because of this, teams using traditional service principal credentials need a defined procedure for tracking expiration dates and rotating secrets proactively, rather than discovering the expiration when production authentication starts failing.

8. Can Apps4Rent help design our Azure identity and access strategy?

   Yes. Apps4Rent’s Azure consulting services include auditing existing authentication methods, identifying opportunities to replace service principal secrets with managed identities, designing least-privilege RBAC assignments, and building identity management into landing zone architecture from the start, with ongoing governance available through our Azure managed services.