ARM Template vs Terraform for Azure: Key Differences and Usage

Both ARM templates and Terraform automate Azure infrastructure deployment, but ARM templates are native JSON files tightly integrated with Azure, while Terraform is a multi-cloud tool using HCL language with state management. Choose ARM templates for Azure-specific, declarative deployments and Terraform for multi-cloud flexibility and advanced state handling.

Quick Comparison

This table summarizes key factors comparing ARM templates and Terraform for Azure deployments.

Factor	ARM Template	Terraform
Language	JSON	HashiCorp Configuration Language (HCL)
Cloud Support	Azure only	Multi-cloud (Azure, AWS, GCP, etc.)
State Management	No external state file; Azure tracks deployment state	Maintains local or remote state file to track resources
Modularity	Supports nested templates but can be complex	Supports modules for reusable components easily
Learning Curve	Steeper due to JSON syntax and Azure specifics	Simpler syntax and widely used across clouds
Tooling & Community	Azure native tooling and documentation	Large open-source community and plugins

Key Differences

ARM templates are native Azure JSON files that describe resources declaratively. They deploy resources directly through Azure Resource Manager without needing external state files. This makes them tightly integrated but less flexible for complex workflows.

Terraform uses HCL, a simpler and more readable language, and manages state files locally or remotely to track resource changes. This state management allows Terraform to plan changes before applying them, reducing errors and enabling multi-cloud deployments.

While ARM templates support nested templates for reuse, Terraform offers modules that are easier to organize and share. Terraform also has a broader ecosystem with providers for many clouds and services, making it a better choice for hybrid or multi-cloud environments.

Code Comparison

Here is how to create an Azure Storage Account using an ARM template.

json

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [
    {
      "type": "Microsoft.Storage/storageAccounts",
      "apiVersion": "2022-09-01",
      "name": "examplestorageacct",
      "location": "eastus",
      "sku": {
        "name": "Standard_LRS"
      },
      "kind": "StorageV2",
      "properties": {}
    }
  ]
}

Output

Deploys an Azure Storage Account named 'examplestorageacct' in East US with Standard_LRS SKU.

Terraform Equivalent

Here is how to create the same Azure Storage Account using Terraform.

hcl

provider "azurerm" {
  features {}
}

resource "azurerm_storage_account" "example" {
  name                     = "examplestorageacct"
  resource_group_name      = "example-rg"
  location                 = "eastus"
  account_tier             = "Standard"
  account_replication_type = "LRS"
  account_kind             = "StorageV2"
}

Output

Creates an Azure Storage Account named 'examplestorageacct' in resource group 'example-rg' located in East US with Standard_LRS replication.

When to Use Which

Choose ARM templates when you want native Azure integration, need to use Azure-specific features immediately, or prefer JSON declarative syntax tightly coupled with Azure Resource Manager.

Choose Terraform when you want multi-cloud support, easier syntax, advanced state management, reusable modules, or plan to manage infrastructure beyond Azure. Terraform is also better for teams needing collaboration and versioned state.

Key Takeaways

ARM templates are Azure-native JSON files best for Azure-only deployments with tight integration.

Terraform uses HCL and manages state files, enabling multi-cloud and complex infrastructure management.

Terraform's modularity and community support make it ideal for reusable and cross-cloud infrastructure.

Use ARM templates for quick Azure-specific deployments; use Terraform for flexibility and multi-cloud needs.