terraform/website/docs/language/meta-arguments/count.html.md

---
layout: "language"
page_title: "The count Meta-Argument - Configuration Language"
---

# The `count` Meta-Argument

-> **Version note:** Module support for `count` was added in Terraform 0.13, and
previous versions can only use it with resources.

-> **Note:** A given resource or module block cannot use both `count` and `for_each`.

> **Hands-on:** Try the [Manage Similar Resources With Count](https://learn.hashicorp.com/tutorials/terraform/count?in=terraform/0-13&utm_source=WEBSITE&utm_medium=WEB_IO&utm_offer=ARTICLE_PAGE&utm_content=DOCS) tutorial on HashiCorp Learn.

By default, a [resource block](/docs/language/resources/syntax.html) configures one real
infrastructure object. (Similarly, a
[module block](/docs/language/modules/syntax.html) includes a
child module's contents into the configuration one time.)
However, sometimes you want to manage several similar objects (like a fixed
pool of compute instances) without writing a separate block for each one.
Terraform has two ways to do this:
`count` and [`for_each`](/docs/language/meta-arguments/for_each.html).

If a resource or module block includes a `count` argument whose value is a whole number,
Terraform will create that many instances.

## Basic Syntax

`count` is a meta-argument defined by the Terraform language. It can be used
with modules and with every resource type.

The `count` meta-argument accepts a whole number, and creates that many
instances of the resource or module. Each instance has a distinct infrastructure object
associated with it, and each is separately created,
updated, or destroyed when the configuration is applied.

```hcl
resource "aws_instance" "server" {
  count = 4 # create four similar EC2 instances

  ami           = "ami-a1b2c3d4"
  instance_type = "t2.micro"

  tags = {
    Name = "Server ${count.index}"
  }
}
```

## The `count` Object

In blocks where `count` is set, an additional `count` object is
available in expressions, so you can modify the configuration of each instance.
This object has one attribute:

- `count.index` — The distinct index number (starting with `0`) corresponding
  to this instance.

## Using Expressions in `count`

The `count` meta-argument accepts numeric [expressions](/docs/language/expressions/index.html).
However, unlike most arguments, the `count` value must be known
_before_ Terraform performs any remote resource actions. This means `count`
can't refer to any resource attributes that aren't known until after a
configuration is applied (such as a unique ID generated by the remote API when
an object is created).

## Referring to Instances

When `count` is set, Terraform distinguishes between the block itself
and the multiple _resource or module instances_ associated with it. Instances are
identified by an index number, starting with `0`.

- `<TYPE>.<NAME>` or `module.<NAME>` (for example, `aws_instance.server`) refers to the resource block.
- `<TYPE>.<NAME>[<INDEX>]` or `module.<NAME>[<INDEX>]` (for example, `aws_instance.server[0]`,
  `aws_instance.server[1]`, etc.) refers to individual instances.

This is different from resources and modules without `count` or `for_each`, which can be
referenced without an index or key.

Similarly, resources from child modules with multiple instances are prefixed
with `module.<NAME>[<KEY>]` when displayed in plan output and elsewhere in the UI.
For a module without `count` or `for_each`, the address will not contain
the module index as the module's name suffices to reference the module.

-> **Note:** Within nested `provisioner` or `connection` blocks, the special
`self` object refers to the current _resource instance,_ not the resource block
as a whole.

## When to Use `for_each` Instead of `count`

If your instances are almost identical, `count` is appropriate. If some
of their arguments need distinct values that can't be directly derived from an
integer, it's safer to use `for_each`.

Before `for_each` was available, it was common to derive `count` from the
length of a list and use `count.index` to look up the original list value:

```hcl
variable "subnet_ids" {
  type = list(string)
}

resource "aws_instance" "server" {
  # Create one instance for each subnet
  count = length(var.subnet_ids)

  ami           = "ami-a1b2c3d4"
  instance_type = "t2.micro"
  subnet_id     = var.subnet_ids[count.index]

  tags = {
    Name = "Server ${count.index}"
  }
}
```

This was fragile, because the resource instances were still identified by their
_index_ instead of the string values in the list. If an element was removed from
the middle of the list, every instance _after_ that element would see its
`subnet_id` value change, resulting in more remote object changes than intended.
Using `for_each` gives the same flexibility without the extra churn.