Transform

The optional Transform section specifies one or more macros that CloudFormation uses to process your template in some way.

Macros can perform simple tasks like finding and replacing text, or they can make more extensive transformations to the entire template. CloudFormation executes macros in the order that they're specified. When you create a change set, CloudFormation generates a change set that includes the processed template content. You can then review the changes and execute the change set. For more information about how macros work, see Using AWS CloudFormation macros to perform custom processing on templates.

CloudFormation also supports transforms, which are macros hosted by CloudFormation. CloudFormation treats these transforms the same as any macros you create in terms of execution order and scope. For more information, see Transform reference.

To declare multiple macros, use a list format and specify one or more macros.

For example, in the template sample below, CloudFormation evaluates MyMacro and then AWS::Serverless, both of which can process the contents of the entire template because of their inclusion in the Transform section.

// Start of processable content for MyMacro and AWS::Serverless
Transform:
  - MyMacro
  - 'AWS::Serverless'
Resources:
  WaitCondition:
    Type: 'AWS::CloudFormation::WaitCondition'
  MyBucket:
    Type: 'AWS::S3::Bucket'
    Properties: 
        BucketName: MyBucket 
        Tags: [{"key":"value"}] 
        CorsConfiguration:[] 
  MyEc2Instance:
    Type: 'AWS::EC2::Instance' 
    Properties:
        ImageID: "ami-123"
// End of processable content for MyMacro and AWS::Serverless