Terragrunt vs Terraform Workspaces: Key Differences and Usage

Both Terragrunt and Terraform workspaces help manage multiple infrastructure environments, but Terraform workspaces isolate state files within a single configuration, while Terragrunt manages multiple configurations and environments with reusable code and better DRY principles. Terragrunt offers more flexibility for complex setups, whereas Terraform workspaces are simpler for basic environment separation.

Quick Comparison

This table summarizes the main differences between Terragrunt and Terraform workspaces for managing infrastructure environments.

Feature	Terraform Workspaces	Terragrunt
Purpose	Isolate state files within one Terraform config	Manage multiple Terraform configs and environments
State Management	Separate state per workspace in same backend	Separate state per environment with configurable backend
Code Reuse	Limited, same config shared across workspaces	Strong, uses modules and includes for DRY code
Complexity Handling	Simple environment separation	Supports complex multi-environment and multi-region setups
Learning Curve	Lower, built-in Terraform feature	Higher, requires learning Terragrunt syntax
Use Case	Basic environment isolation (dev, prod)	Advanced environment and infrastructure orchestration

Key Differences

Terraform workspaces are a built-in feature that lets you switch between different state files within the same Terraform configuration. This means you can have multiple environments like dev and prod using the same code but storing their state separately. However, the code itself remains the same, so managing differences between environments requires conditional logic inside the Terraform files.

Terragrunt is a wrapper tool that helps organize multiple Terraform configurations. It encourages reusing code by calling shared modules and managing environment-specific settings in separate folders or files. Terragrunt handles backend configuration, dependencies, and variable injection, making it easier to maintain complex setups with many environments or regions.

In short, Terraform workspaces focus on simple state isolation, while Terragrunt provides a higher-level structure for managing multiple Terraform projects with reusable code and better environment separation.

Code Comparison

Here is how you define and use Terraform workspaces to manage two environments with the same configuration.

terraform

terraform {
  backend "s3" {
    bucket = "my-terraform-state"
    key    = "app/terraform.tfstate"
    region = "us-east-1"
  }
}

variable "instance_count" {
  type    = number
  default = 1
}

resource "aws_instance" "example" {
  ami           = "ami-12345678"
  instance_type = "t2.micro"
  count         = var.instance_count
}

# Use workspace to set instance count
locals {
  instance_count = terraform.workspace == "prod" ? 3 : 1
}

variable "instance_count" {
  default = local.instance_count
}

Output

When you run `terraform workspace select prod`, it uses 3 instances; in `default` workspace, it uses 1 instance.

Terragrunt Equivalent

This example shows how Terragrunt manages two environments with separate folders and shared modules.

hcl

# terragrunt.hcl in root folder
remote_state {
  backend = "s3"
  config = {
    bucket = "my-terraform-state"
    region = "us-east-1"
    key    = "${path_relative_to_include()}/terraform.tfstate"
  }
}

# dev/terragrunt.hcl
include {
  path = find_in_parent_folders()
}

inputs = {
  instance_count = 1
}

# prod/terragrunt.hcl
include {
  path = find_in_parent_folders()
}

inputs = {
  instance_count = 3
}

Output

Running `terragrunt apply` in dev uses 1 instance; in prod uses 3 instances, with separate state files.

When to Use Which

Choose Terraform workspaces if you have a simple setup with a few environments that share almost identical infrastructure code and you want quick state isolation without extra tools.

Choose Terragrunt when you manage multiple environments, regions, or complex infrastructure that benefits from reusable modules, clear environment separation, and easier backend configuration. Terragrunt scales better for large teams and projects.

Key Takeaways

Terraform workspaces isolate state files within one configuration but share the same code.

Terragrunt manages multiple Terraform configurations with reusable code and better environment separation.

Use Terraform workspaces for simple environment isolation and Terragrunt for complex multi-environment setups.

Terragrunt requires learning its syntax but offers more flexibility and DRY principles.

Terraform workspaces are built-in and easier for beginners to start with.