Configure App Service plans for zone redundancy

Azure App Service provides built-in reliability features to help ensure that your applications remain available and resilient. This article describes how to create an App Service plan that includes zone redundancy. It also covers how to disable and enable zone redundancy on existing plans and how to check for zone redundancy support. For more information about zone redundancy, see Reliability in App Service.

Important

Zone redundancy distributes App Service plan instances across availability zones; it doesn't create guaranteed app replicas. If perSiteScaling is true and an app or deployment slot has a worker limit of 1, don't infer that the app or slot has a second hot replica. Limits of 2 or more permit placement on multiple distinct plan workers but don't guarantee that those instances span physical zones. Review per-app scaling and Reliability in App Service when you design the workload.

Create a new zone-redundant App Service plan

To create a new App Service plan that includes zone redundancy, follow the appropriate steps.

Follow the guidance to create an App Service plan. Make sure to select Enabled for Zone redundancy.

Screenshot of zone redundancy enablement during App Service plan creation in the Azure portal.

Set the --zone-redundant argument.
Set the --number-of-workers argument, which is the number of instances, to a value of 2 or more.

az appservice plan create \
    -n <app-service-plan-name> \
    -g <resource-group-name> \
    --zone-redundant \
    --number-of-workers 2 \
    --sku P1V3

Set the zoneRedundant property to true.
Set the sku.capacity property to a value of 2 or more. If you don't define the sku.capacity property, the value defaults to 1.

resource appServicePlan 'Microsoft.Web/serverfarms@2024-11-01' = {
    name: appServicePlanName
    location: location
    sku: {
        name: sku
        capacity: 2
    }
    kind: 'linux'
    properties: {
        reserved: true
        zoneRedundant: true
    }
}

Set zone redundancy for an existing App Service plan

To enable zone redundancy on an existing App Service plan, check for zone redundancy support.
If your App Service plan supports zone redundancy, use the Azure portal, the Azure CLI, or Bicep and Azure Resource Manager to enable or disable it.

Important

Before you enable zone redundancy, record the current plan capacity and scaling mode. If per-app scaling is enabled, review the configured worker limit for each app and deployment slot. A limit of 1 doesn't provide a simultaneous replica in another zone. For Rules Based scaling, ensure that every applicable autoscale profile has minimum, default, and maximum capacities of at least 2.
1. In the Azure portal, go to your App Service plan.
2. Select Settings > Scale out (App Service plan) in the left navigation pane.
3. Follow the instructions for the scaling mode configured for the plan:
  - Manual: If Instance count is less than 2, increase it to 2; preserve a higher value. Select Zone Redundancy, and then save your changes.
  - Automatic: Minimum instances is managed and unavailable in the portal. Select Zone Redundancy, save your changes, and then confirm that the resulting plan capacity is at least 2.
  - Rules Based: You can't perform this workflow in the portal. First, separately update every applicable autoscale profile so that its minimum, default, and maximum are each at least 2, preserving higher values. Then use the Azure CLI or Bicep and Azure Resource Manager to enable zone redundancy.
For Manual or Automatic scaling, to disable zone redundancy, deselect Zone Redundancy, and then save your changes.
Important

For Rules Based scaling, first update every applicable autoscale profile so that its minimum, default, and maximum are each at least 2. Preserve higher values. Changing only the current sku.capacity doesn't prevent autoscale from later requesting a lower capacity.
- To enable zone redundancy when the current sku.capacity is already 2 or greater, set only the zoneRedundant property to true. This update preserves the current capacity.
```
az appservice plan update \
   -n <app-service-plan-name> \
   -g <resource-group-name> \
   --set zoneRedundant=true
```
- If the current sku.capacity is less than 2, raise it to 2 while enabling zone redundancy.
```
az appservice plan update \
   -n <app-service-plan-name> \
   -g <resource-group-name> \
   --set zoneRedundant=true sku.capacity=2
```
- To disable zone redundancy, set the zoneRedundant property to false.
```
az appservice plan update \
   -n <app-service-plan-name> \
   -g <resource-group-name> \
   --set zoneRedundant=false
```
Important

For Rules Based scaling, update the autoscale configuration separately before this deployment. Every applicable profile must have minimum, default, and maximum values of at least 2, with higher values preserved. The sku.capacity expression in this template doesn't update autoscale profiles.
- To enable zone redundancy, set the zoneRedundant property to true.
- Set currentPlanCapacity to the plan's current configured capacity. The max expression preserves a value that's already 2 or greater and raises only a lower value to 2.
- Keep the current plan values for sku, kind, reserved, and other settings when you adapt the example.
```
param currentPlanCapacity int

resource appServicePlan 'Microsoft.Web/serverfarms@2024-11-01' = {
    name: appServicePlanName
    location: location
    sku: {
        name: sku
        capacity: max(2, currentPlanCapacity)
    }
    kind: 'linux'
    properties: {
        reserved: true
        zoneRedundant: true
    }
}
```
- To disable zone redundancy, set the zoneRedundant property to false.
If your App Service plan is on a scale unit that doesn't support zone redundancy, you can't enable zone redundancy on your plan. Instead, you need to redeploy your apps to a new plan on a different scale unit.

Check for zone redundancy support on an App Service plan

To check whether an existing App Service plan supports zone redundancy, do the following steps:

Determine the maximum number of availability zones that the App Service plan supports by using the Azure portal, the Azure CLI, or Bicep and Resource Manager.
1. In the Azure portal, go to your App Service plan.
2. Select Scale out (App Service plan).
  
  Maximum available zones shows the maximum number of zones that your App Service plan can use.
Query the plan's maximumNumberOfZones property.
```
az appservice plan show \
    -n <app-service-plan-name> \
    -g <resource-group-name> \
    --query properties.maximumNumberOfZones
```
Query the plan's maximumNumberOfZones property.
```
resource appServicePlan 'Microsoft.Web/serverfarms@2024-11-01' existing = {
    name: '<app-service-plan-name>'
}

#disable-next-line BCP083
output maximumNumberOfZones int = appServicePlan.properties.maximumNumberOfZones
```
Compare the number with the following table to determine whether your plan supports zone redundancy.

Maximum number of zones Zone redundancy support

More than 1 Supported

Equal to 1 Not supported*

* If you use a plan or a stamp that doesn't support availability zones, you must create a new App Service plan in a new resource group. This setup ensures that your deployment lands on App Service infrastructure that supports availability zones.

Maximum number of zones	Zone redundancy support
More than 1	Supported
Equal to 1	Not supported*

View physical zones for an App Service plan

When you have a zone-redundant App Service plan, the platform places plan instances across physical availability zones. Use the Azure portal or the Azure CLI to inspect the physical zone reported for an app's currently observed instances.

Note

Observed physicalZone values are point-in-time placement information. They don't prove that hidden app replicas exist or guarantee physical-zone diversity for an app or deployment slot. By using per-app scaling, an app can run on fewer instances than the plan.

In the Azure portal, go to the App Service app that you want to inspect.
Select Health check.
Select Instances to view the physical zone placement for each of your instances.

Use the REST API, which returns the physicalZone value for each currently observed instance of the specified app.

az rest --method get --url /subscriptions/{subscriptionId}/resourceGroups/{resourceGroup}/providers/Microsoft.Web/sites/{appName}/instances?api-version=2024-04-01

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Last updated on 2026-08-31