Azure Bicep

Overview

Bicep is Azure's domain-specific language for deploying Azure resources declaratively. It compiles to ARM JSON but provides a cleaner syntax with type safety, modules, and IDE support. Bicep is the recommended replacement for authoring ARM templates directly.

Basic Template

@description('The Azure region for all resources')
param location string = resourceGroup().location

@allowed(['dev', 'staging', 'prod'])
param environment string = 'dev'

resource storageAccount 'Microsoft.Storage/storageAccounts@2023-01-01' = {
  name: 'st${uniqueString(resourceGroup().id)}${environment}'
  location: location
  sku: {
    name: 'Standard_LRS'
  }
  kind: 'StorageV2'
  properties: {
    minimumTlsVersion: 'TLS1_2'
    supportsHttpsTrafficOnly: true
  }
}

resource appServicePlan 'Microsoft.Web/serverfarms@2023-01-01' = {
  name: 'asp-${environment}'
  location: location
  sku: {
    name: environment == 'prod' ? 'P1v3' : 'B1'
  }
}

resource webApp 'Microsoft.Web/sites@2023-01-01' = {
  name: 'app-${environment}-${uniqueString(resourceGroup().id)}'
  location: location
  properties: {
    serverFarmId: appServicePlan.id
    siteConfig: {
      minTlsVersion: '1.2'
    }
  }
}

output webAppUrl string = 'https://${webApp.properties.defaultHostName}'
output storageAccountId string = storageAccount.id

Modules

Reusable components in separate .bicep files:

// modules/storage.bicep
param name string
param location string
param sku string = 'Standard_LRS'

resource storage 'Microsoft.Storage/storageAccounts@2023-01-01' = {
  name: name
  location: location
  sku: { name: sku }
  kind: 'StorageV2'
}

output id string = storage.id
output name string = storage.name

Consume in the main template:

module storage 'modules/storage.bicep' = {
  name: 'storageDeployment'
  params: {
    name: 'stmyapp${environment}'
    location: location
    sku: environment == 'prod' ? 'Standard_GRS' : 'Standard_LRS'
  }
}

Deployment

# Deploy to a resource group
az deployment group create \
  --resource-group my-rg \
  --template-file main.bicep \
  --parameters environment=prod

# What-if (preview changes)
az deployment group what-if \
  --resource-group my-rg \
  --template-file main.bicep

# Deploy to subscription scope
az deployment sub create \
  --location eastus \
  --template-file main.bicep

Key Features

Best Practices

• Always use what-if to preview changes before deploying.
• Use modules to break large templates into reusable, testable components.
• Use parameter decorators (@allowed, @minLength, @description) for validation and documentation.
• Reference existing resources with the existing keyword instead of hardcoding resource IDs.
• Use uniqueString(resourceGroup().id) for globally unique names (storage accounts, web apps).
• Pin API versions on resources for predictable behavior.
• Use Bicep instead of ARM JSON — it compiles to identical output with better readability.