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Convert JSON CloudFormation templates to the new YAML syntax. This includes converting all Fn::* and Ref JSON functions to !* yaml node type functions.

In addition, cfnjsontoyaml tries to make a best guess at when Fn::Join functions should automatically be converted to !Sub.

Convert Long JSON to compact YAML

This utility not only converts from JSON to yaml, it will use the new short yaml syntax, and attempt to convert Fn::Join to !Sub, resulting in shorter, more compact syntax.

For example, and IAM role can be converted from 127 lines of JSON cloudformation to 30 lines of yaml.




cfn-json-to-yaml reads either from standard in, or takes the first argument as the template to ingest and prints the yaml converted template to stdout.

$ pip install cfnjsontoyaml
$ cat my_template.json | cfn-json-to-yaml


APIGateway Method with lambda proxy

In some cases, we can halve the number of lines, while still maintaining readability. Here, we convert 48 lines of JSON to 19 lines of YAML. #### JSON

  "Resources": {
    "MappingReferenceMethod": {
      "Type": "AWS::ApiGateway::Method",
      "DependsOn": [
      "Properties": {
        "RestApiId": {
          "Ref": "RestApi"
        "ResourceId": {
          "Ref": "MappingReferenceResource"
        "HttpMethod": "POST",
        "AuthorizationType": "NONE",
        "ApiKeyRequired": true,
        "RequestParameters": {
          "method.request.header.x-api-key": true
        "Integration": {
          "Type": "AWS_PROXY",
          "Uri": {
            "Fn::Join": [
                  "Ref": "AWS::Region"
                  "Fn::GetAtt": [
          "IntegrationHttpMethod": "POST",
          "PassthroughBehavior": "when_no_templates"


    Type: AWS::ApiGateway::Method
      ApiKeyRequired: true
      AuthorizationType: NONE
      HttpMethod: POST
        IntegrationHttpMethod: POST
        PassthroughBehavior: when_no_templates
        Type: AWS_PROXY
        Uri: !Sub "arn:aws:apigateway:${AWS::Region}:lambda:path/2015-03-31/functions/${LambdaFunctionMappingReference.Arn}/invocations"
        method.request.header.x-api-key: true
      ResourceId: !Ref "MappingReferenceResource"
      RestApiId: !Ref "RestApi"
    - LambdaInvokePermissionMappingReference


There are a wide range of combinations for functions in cloudformation. If you come across a template which does not render correctly, please try and isolate the fragment of json which is causing issues, and create an issue in github .

If you’d like to be a bit more helpful, you can fork the repository, create a branch, and add a json/yaml snippet to with the next sequential number. The smaller the json/yaml snippet you can provide the quicker I can fix it. :-)

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