Conditional deployments in Bicep with the if expression

To optionally deploy a resource or module in Bicep, use the if expression. An if expression includes a condition that resolves to true or false. When the if condition is true, the resource is deployed. When the value is false, the resource isn't created. You can only apply the value to the whole resource or module.

Note

Conditional deployment doesn't cascade to child resources. If you want to conditionally deploy a resource and its child resources, you must apply the same condition to each resource type.

Training resources

If you would rather learn about conditions through step-by-step guidance, see Build flexible Bicep templates by using conditions and loops.

Define condition for deployment

In Bicep, you can conditionally deploy a resource by passing in a parameter that specifies if the resource is deployed. Test the condition with an if expression in the resource declaration. The following example shows the syntax for an if expression in a Bicep file. It conditionally deploys a Domain Name System (DNS) zone. When deployZone is true, it deploys the DNS zone. When deployZone is false, it skips deploying the DNS zone.

param deployZone bool

resource dnsZone 'Microsoft.Network/dnsZones@2023-07-01-preview' = if (deployZone) {
  name: 'myZone'
  location: 'global'
}

The following example conditionally deploys a module:

param deployZone bool

module dnsZone 'dnszones.bicep' = if (deployZone) {
  name: 'myZoneModule'
}

You can use conditions with dependency declarations. For explicit dependencies, Azure Resource Manager automatically removes them from the required dependencies when the resource isn't deployed. For implicit dependencies, referencing a property of a conditional resource is allowed but might produce a deployment error.

New or existing resource

You can use conditional deployment to create a new resource or use an existing one. The following example shows how to deploy a new storage account or use an existing storage account.

param storageAccountName string
param location string = resourceGroup().location

@allowed([
  'new'
  'existing'
])
param newOrExisting string = 'new'

resource saNew 'Microsoft.Storage/storageAccounts@2023-04-01' = if (newOrExisting == 'new') {
  name: storageAccountName
  location: location
  sku: {
    name: 'Standard_LRS'
  }
  kind: 'StorageV2'
}

resource saExisting 'Microsoft.Storage/storageAccounts@2023-04-01' existing = if (newOrExisting == 'existing') {
  name: storageAccountName
}

output storageAccountId string = ((newOrExisting == 'new') ? saNew.id : saExisting.id)

When the parameter newOrExisting is set to new, the condition evaluates to true. The storage account is deployed. Otherwise, the existing storage account is used.

Warning

If you reference a conditionally deployed resource but the resource isn't deployed, you get an error. The error message states that the resource isn't defined in the template.

Runtime functions

If you use a reference or list function with a resource that you specify for conditional deployment, the function gets evaluated. If the resource isn't deployed, you get an error.

Use the conditional expression ?: operator to ensure that the function is only evaluated for conditions when the resource is deployed. The following example template shows how to use this function with expressions that are only conditionally valid.

param vmName string
param location string
param logAnalytics string = ''

resource vmName_omsOnboarding 'Microsoft.Compute/virtualMachines/extensions@2024-03-01' = if (!empty(logAnalytics)) {
  name: '${vmName}/omsOnboarding'
  location: location
  properties: {
    publisher: 'Microsoft.EnterpriseCloud.Monitoring'
    type: 'MicrosoftMonitoringAgent'
    typeHandlerVersion: '1.0'
    autoUpgradeMinorVersion: true
    settings: {
      workspaceId: ((!empty(logAnalytics)) ? reference(logAnalytics, '2022-10-01').customerId : null)
    }
    protectedSettings: {
      workspaceKey: ((!empty(logAnalytics)) ? listKeys(logAnalytics, '2022-10-01').primarySharedKey : null)
    }
  }
}

output mgmtStatus string = ((!empty(logAnalytics)) ? 'Enabled monitoring for VM!' : 'Nothing to enable')

Next steps

• For recommendations about creating Bicep files, see Best practices for Bicep.
• To create multiple instances of a resource, see Iterative loops in Bicep.