AWS CloudFormation
User Guide (API Version 2010-05-15)
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The intrinsic function Fn::GetAZs returns an array that lists Availability Zones for a specified region. Because customers have access to different Availability Zones, the intrinsic function Fn::GetAZs enables template authors to write templates that adapt to the calling user's access. That way you don't have to hard-code a full list of Availability Zones for a specified region.


For the EC2-Classic platform, the Fn::GetAZs function returns all Availability Zones for a region. For the EC2-VPC platform, the Fn::GetAZs function returns only Availability Zones that have a default subnet unless none of the Availability Zones has a default subnet; in that case, all Availability Zones are returned.

IAM permissions

The permissions that you need in order to use the Fn::GetAZs function depend on the platform in which you're launching Amazon EC2 instances. For both platforms, you need permissions to the Amazon EC2 DescribeAvailabilityZones and DescribeAccountAttributes actions. For EC2-VPC, you also need permissions to the Amazon EC2 DescribeSubnets action.


"Fn::GetAZs" : "region"



The name of the region for which you want to get the Availability Zones.

You can use the AWS::Region pseudo parameter to specify the region in which the stack is created. Specifying an empty string is equivalent to specifying AWS::Region.

Return Value

The list of Availability Zones for the region.


{ "Fn::GetAZs" : "" }
{ "Fn::GetAZs" : { "Ref" : "AWS::Region" } }
{ "Fn::GetAZs" : "us-east-1" }

For the previous examples, AWS CloudFormation evaluates Fn::GetAZs to the following array—assuming that the user has created the stack in the us-east-1 region:

[ "us-east-1a", "us-east-1b", "us-east-1c" ]

Supported Functions

You can use the Ref function in the Fn::GetAZs function.