When writing Terraform code to manage cloud infrastructure, we often deal with multiple similar resources — for example, a group of EC2 instances, multiple storage accounts, or several subnets.

So how do we easily access the same attribute (like ID or name) from all of them?

This is where Terraform’s splat expressions shine.

In this blog, we’ll break down:

• What splat expressions are

• When and why to use them

• Simple examples using count and for_each

• When to use for loop instead

• Tips and best practices

What Is a Splat Expression?

In Terraform, a splat expression uses the asterisk symbol (*) to quickly extract values from a list or map of resources.

In short: Use [*] to grab the same property from all resources in a group*.*

Scenario 1: Using count to Create Multiple Resources

Let’s say you want to create 3 EC2 instances.

resource "aws_instance" "example" {
  count         = 3
  ami           = "ami-12345678"
  instance_type = "t2.micro"
}

Each instance will have its own ID, IP, and so on.

Now, if you want to get all 3 instance IDs, instead of writing:

[
  aws_instance.example[0].id,
  aws_instance.example[1].id,
  aws_instance.example[2].id
]

You can just write:

output "instance_ids" {
  value = aws_instance.example[*].id
}

This is a splat expression.

It goes through every instance in the list and pulls out the .id value — and gives you a list like:

["i-abc123", "i-def456", "i-ghi789"]

Scenario 2: Using for_each to Create Multiple Resources

Let’s create multiple S3 buckets using for_each:

resource "aws_s3_bucket" "example" {
  for_each = toset(["my-bucket-1", "my-bucket-2"])
  bucket   = each.key
  acl      = "private"
}

Now you want the IDs of all buckets. Since for_each uses a map, you can’t directly use the [*] shortcut. Instead, combine it with values():

output "bucket_ids" {
  value = values(aws_s3_bucket.example)[*].id
}

Here:

• values(...) turns the map into a list

• [*].id extracts all IDs from that list

Behind the Scenes — What Does [*] Do?

A splat expression is just a shortcut. It’s equivalent to a loop that collects a specific attribute from every item in the list.

So this:

aws_instance.example[*].id

Is roughly like:

[for instance in aws_instance.example : instance.id]

When to Use a for Expression Instead

If you want to do something more custom, like filtering or transforming values, use a for loop:

output "instance_names" {
  value = [for inst in aws_instance.example : "instance-${inst.id}"]
}

This gives you a custom list like:

["instance-i-abc123", "instance-i-def456", ...]

Summary

FeatureDescription[*] (splat)Shortcut to extract a field from a list of resourcesWith countDirectly use resource_name[*].fieldWith for_eachUse values(resource_name)[*].fieldPrefer for loopWhen you need filtering or custom formatting

Final Tip

If you’re working with many dynamic resources, splat expressions make your Terraform code clean, readable, and easy to maintain.

They save time and reduce repetition — especially when you’re managing infrastructure at scale.