Outputs - AWS CloudFormation
SyntaxExamples

Outputs

The optional Outputs section declares output values for the stack. These output values can be used in various ways:

  • Cross-stack references – You can import output values into other stacks to create references between stacks. This is helpful when you need to share resources or configurations across multiple stacks.

  • Capture important details about your resources – An output is a convenient way to capture important information about your resources. For example, you can output the S3 bucket name for a stack to make the bucket easier to find. You can view output values in the Outputs tab of the CloudFormation console or by using the describe-stacks CLI command.

Important

CloudFormation doesn't redact or obfuscate any information you include in the Outputs section. We strongly recommend you don't use this section to output sensitive information, such as passwords or secrets.

Output values are available after the stack operation is complete. Stack output values aren't available when a stack status is in any of the IN_PROGRESS status. We don't recommend establishing dependencies between a service runtime and the stack output value because output values might not be available at all times.

Syntax

The Outputs section consists of the key name Outputs. You can declare a maximum of 200 outputs in a template.

The following example demonstrates the structure of the Outputs section.

JSON

Use braces to enclose all output declarations. Delimit multiple outputs with commas.

"Outputs" : {
  "Logical ID of resource" : {
    "Description" : "Information about the value",
    "Value" : "Value to return",
    "Export" : {
      "Name" : "Name of resource to export"
    }
  }
}

YAML

Outputs:
  Logical ID of resource:
    Description: Information about the value
    Value: Value to return
    Export:
      Name: Name of resource to export

Output fields

The Outputs section can include the following fields.

Logical ID (also called logical name)

An identifier for the current output. The logical ID must be alphanumeric (a–z, A–Z, 0–9) and unique within the template.

Description (optional)

A String type that describes the output value. The value for the description declaration must be a literal string that's between 0 and 1024 bytes in length. You can't use a parameter or function to specify the description.

Value (required)

The value of the property returned by the aws cloudformation describe-stacks command. The value of an output can include literals, parameter references, pseudo-parameters, a mapping value, or intrinsic functions.

Export (optional)

The name of the resource output to be exported for a cross-stack reference.

Note

The following restrictions apply to cross-stack references:

  • For each AWS account, Export names must be unique within a Region.

  • You can't create cross-stack references across Regions. You can use the intrinsic function Fn::ImportValue to import only values that have been exported within the same Region.

  • For outputs, the value of the Name property of an Export can't use Ref or GetAtt functions that depend on a resource.

    Similarly, the ImportValue function can't include Ref or GetAtt functions that depend on a resource.

  • After another stack imports an output value, you can't delete the stack that is exporting the output value or modify the exported output value. All the imports must be removed before you can delete the exporting stack or modify the output value.

You can use intrinsic functions to customize the Name value of an export.

To associate a condition with an output, define the condition in the Conditions section of the template.

Examples

The following examples illustrate how stack output works.

Stack output

In the following example, the output named BackupLoadBalancerDNSName returns the DNS name for the resource with the logical ID BackupLoadBalancer only when the CreateProdResources condition is true. The output named InstanceID returns the ID of the EC2 instance with the logical ID EC2Instance.

JSON

"Outputs" : {
  "BackupLoadBalancerDNSName" : {
    "Description": "The DNSName of the backup load balancer",  
    "Value" : { "Fn::GetAtt" : [ "BackupLoadBalancer", "DNSName" ]},
    "Condition" : "CreateProdResources"
  },
  "InstanceID" : {
    "Description": "The Instance ID",  
    "Value" : { "Ref" : "EC2Instance" }
  }
}

YAML

Outputs:
  BackupLoadBalancerDNSName:
    Description: The DNSName of the backup load balancer
    Value: !GetAtt BackupLoadBalancer.DNSName
    Condition: CreateProdResources
  InstanceID:
    Description: The Instance ID
    Value: !Ref EC2Instance

Customize export name using Fn::Sub

In the following examples, the output named StackVPC returns the ID of a VPC, and then exports the value for cross-stack referencing with the name VPCID appended to the stack's name.

JSON

"Outputs" : {
  "StackVPC" : {
    "Description" : "The ID of the VPC",
    "Value" : { "Ref" : "MyVPC" },
    "Export" : {
      "Name" : {"Fn::Sub": "${AWS::StackName}-VPCID" }
    }
  }
}

YAML

Outputs:
  StackVPC:
    Description: The ID of the VPC
    Value: !Ref MyVPC
    Export:
      Name: !Sub "${AWS::StackName}-VPCID"

For more information about the Fn::Sub function, see Fn::Sub.

Customize export name using Fn::Join

You can also use the Fn::Join function to construct values based on parameters, resource attributes, and other strings.

The following examples use the Fn::Join function to customize the export name instead of the Fn::Sub function. The example Fn::Join function concatenates the stack name with the name VPCID using a colon as a separator.

JSON

"Outputs" : {
  "StackVPC" : {
    "Description" : "The ID of the VPC",
    "Value" : { "Ref" : "MyVPC" },
    "Export" : {
      "Name" : { "Fn::Join" : [ ":", [ { "Ref" : "AWS::StackName" }, "VPCID" ] ] }
    }
  }
}

YAML

Outputs:
  StackVPC:
    Description: The ID of the VPC
    Value: !Ref MyVPC
    Export:
      Name: !Join [ ":", [ !Ref "AWS::StackName", VPCID ] ]

For more information about the Fn::Join function, see Fn::Join.

Return a URL constructed using Fn::Join

In the following example for a template that creates a WordPress site, InstallURL is the string returned by a Fn::Join function call that concatenates http://, the DNS name of the resource ElasticLoadBalancer, and /wp-admin/install.php. The output value would be similar to the following:

http://mywptests-elasticl-1gb51l6sl8y5v-206169572.aws-region.elb.amazonaws.com/wp-admin/install.php

JSON

{
    "Outputs": {
        "InstallURL": {
            "Value": {
                "Fn::Join": [
                    "",
                    [
                        "http://",
                        {
                            "Fn::GetAtt": [
                                "ElasticLoadBalancer",
                                "DNSName"
                            ]
                        },
                        "/wp-admin/install.php"
                    ]
                ]
            },
            "Description": "Installation URL of the WordPress website"
        }
    }
}

YAML

Outputs:
  InstallURL:
    Value: !Join 
      - ''
      - - 'http://'
        - !GetAtt 
          - ElasticLoadBalancer
          - DNSName
        - /wp-admin/install.php
    Description: Installation URL of the WordPress website

For more information about the Fn::Join function, see Fn::Join.