Fn::ImportValue

The intrinsic function Fn::ImportValue returns the value of an output exported by another stack. You typically use this function to create cross-stack references. In the following example template snippets, Stack A exports VPC security group values and Stack B imports them.

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.

• You can't delete a stack if another stack references one of its outputs.

• You can't modify or remove an output value that is referenced by another stack.

JSON

Stack A Export

"Outputs" : {
  "PublicSubnet" : {
    "Description" : "The subnet ID to use for public web servers",
    "Value" :  { "Ref" : "PublicSubnet" },
    "Export" : { "Name" : {"Fn::Sub": "${AWS::StackName}-SubnetID" }}
  },
  "WebServerSecurityGroup" : {
    "Description" : "The security group ID to use for public web servers",
    "Value" :  { "Fn::GetAtt" : ["WebServerSecurityGroup", "GroupId"] },
    "Export" : { "Name" : {"Fn::Sub": "${AWS::StackName}-SecurityGroupID" }}
  }
}

YAML

Stack A Export

Outputs:
  PublicSubnet:
    Description: The subnet ID to use for public web servers
    Value:
      Ref: PublicSubnet
    Export:
      Name:
        'Fn::Sub': '${AWS::StackName}-SubnetID'
  WebServerSecurityGroup:
    Description: The security group ID to use for public web servers
    Value:
      'Fn::GetAtt':
        - WebServerSecurityGroup
        - GroupId
    Export:
      Name:
        'Fn::Sub': '${AWS::StackName}-SecurityGroupID'

JSON

Stack B Import

"Resources" : {
  "WebServerInstance" : {
    "Type" : "AWS::EC2::Instance",
    "Properties" : {
      "InstanceType" : "t2.micro",
      "ImageId" : "ami-a1b23456",
      "NetworkInterfaces" : [{
        "GroupSet" : [{"Fn::ImportValue" : {"Fn::Sub" : "${NetworkStackNameParameter}-SecurityGroupID"}}],
        "AssociatePublicIpAddress" : "true",
        "DeviceIndex" : "0",
        "DeleteOnTermination" : "true",
        "SubnetId" : {"Fn::ImportValue" : {"Fn::Sub" : "${NetworkStackNameParameter}-SubnetID"}}
      }]
    }
  }
}

YAML

Stack B Import

Resources:
  WebServerInstance:
    Type: 'AWS::EC2::Instance'
    Properties:
      InstanceType: t2.micro
      ImageId: ami-a1b23456
      NetworkInterfaces:
        - GroupSet:
            - Fn::ImportValue: 
              'Fn::Sub': '${NetworkStackNameParameter}-SecurityGroupID'
          AssociatePublicIpAddress: 'true'
          DeviceIndex: '0'
          DeleteOnTermination: 'true'
          SubnetId: Fn::ImportValue 
            'Fn::Sub': '${NetworkStackNameParameter}-SubnetID'

Declaration

JSON

{ "Fn::ImportValue" : sharedValueToImport }

YAML

You can use the full function name:

Fn::ImportValue: sharedValueToImport

Alternatively, you can use the short form:

!ImportValue sharedValueToImport

Important

You can't use the short form of !ImportValue when it contains the short form of !Sub.

# do not use
!ImportValue
  !Sub '${NetworkStack}-SubnetID' 

Instead, you must use the full function name, for example:

Fn::ImportValue:
  !Sub "${NetworkStack}-SubnetID"

Parameters

sharedValueToImport

The stack output value that you want to import.

Return value

The stack output value.

Example

JSON

{ "Fn::ImportValue" : {"Fn::Sub": "${NetworkStackNameParameter}-SubnetID" } }

YAML

Fn::ImportValue:
  !Sub "${NetworkStackName}-SecurityGroupID"

Supported functions

You can use the following functions in the Fn::ImportValue function. The value of these functions can't depend on a resource.

• Fn::Base64

• Fn::FindInMap

• Fn::If

• Fn::Join

• Fn::Select

• Fn::Sub

• Ref