CloudFormation JSON to YAML Converter

Last updated: • 7 min read

Convert CloudFormation JSON to YAML using cfn-flip, our online converter, or AWS CLI tools. YAML is preferred for CloudFormation templates because it supports comments and shorthand intrinsic functions. This guide covers AWS JSON to YAML conversion methods, validation, and best practices for CloudFormation template management. See our YAML vs JSON comparison on why YAML is often chosen for IaC.

Method 1: Online Converter (Quickest)

The fastest way to convert CloudFormation JSON to YAML:

Open converter: Go to our JSON to YAML tool
Paste CloudFormation JSON: Enter your template
Click Convert: Get YAML output instantly
Download: Save as .yaml file

Note: Our converter handles CloudFormation intrinsic functions like Fn::Ref, Fn::Sub, and Fn::GetAtt correctly.

Method 2: cfn-flip CLI (Recommended)

cfn-flip is the most popular tool for CloudFormation conversion:

# Install cfn-flip
pip install cfn-flip

# Convert JSON to YAML
cfn-flip template.json > template.yaml

# Or use stdin/stdout
cat template.json | cfn-flip > template.yaml

# Convert with specific format
cfn-flip -y template.json   # Force YAML output
cfn-flip -j template.yaml   # Force JSON output

Example CloudFormation Conversion

Input (JSON):

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Description": "S3 bucket for website hosting",
  "Resources": {
    "WebsiteBucket": {
      "Type": "AWS::S3::Bucket",
      "Properties": {
        "BucketName": {"Fn::Sub": "${AWS::StackName}-website"},
        "WebsiteConfiguration": {
          "IndexDocument": "index.html",
          "ErrorDocument": "error.html"
        }
      }
    }
  },
  "Outputs": {
    "BucketURL": {
      "Value": {"Fn::GetAtt": ["WebsiteBucket", "WebsiteURL"]}
    }
  }
}

Output (YAML):

AWSTemplateFormatVersion: '2010-09-09'
Description: S3 bucket for website hosting

Resources:
  WebsiteBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: !Sub ${AWS::StackName}-website
      WebsiteConfiguration:
        IndexDocument: index.html
        ErrorDocument: error.html

Outputs:
  BucketURL:
    Value: !GetAtt WebsiteBucket.WebsiteURL

Method 3: AWS Rain

AWS Rain is a modern CloudFormation CLI tool:

# Install rain
brew install rain  # macOS
# or download from GitHub

# Format and convert template
rain fmt template.json > template.yaml

# Validate template
rain lint template.yaml

CloudFormation YAML to JSON

Convert CloudFormation YAML to JSON when needed:

# Using cfn-flip
cfn-flip -j template.yaml > template.json

# Using yq
yq -o json template.yaml > template.json

# Python one-liner
python -c "import yaml,json,sys; print(json.dumps(yaml.safe_load(open('template.yaml')), indent=2))"

Warning: Comments and shorthand functions (!Ref, !Sub) are converted back to long-form (Fn::Ref, Fn::Sub) when converting to JSON.

Why Use YAML for CloudFormation?

Feature	JSON	YAML
Comments	❌ Not supported	✅ Supported (#)
Intrinsic shorthand	Fn::Ref, Fn::Sub	✅ !Ref, !Sub
Multi-line strings	Escape sequences	✅ \| and > syntax
Readability	Good	✅ Excellent
File size	✅ Smaller (minified)	Similar

CloudFormation YAML Features

Shorthand Intrinsic Functions

# YAML shorthand (preferred)
BucketName: !Sub ${AWS::StackName}-data
RoleArn: !GetAtt MyRole.Arn
SecurityGroup: !Ref MySecurityGroup
AvailabilityZone: !Select [0, !GetAZs '']

# Equivalent JSON long form
# "BucketName": {"Fn::Sub": "${AWS::StackName}-data"}
# "RoleArn": {"Fn::GetAtt": ["MyRole", "Arn"]}
# "SecurityGroup": {"Ref": "MySecurityGroup"}

Comments for Documentation

# Production VPC Configuration
# Last updated: 2025-01-15
# Owner: Platform Team

Resources:
  ProductionVPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16  # /16 gives 65,536 IPs
      Tags:
        - Key: Environment
          Value: Production  # Change to Staging for test

Multi-line User Data

UserData:
  Fn::Base64: |
    #!/bin/bash
    yum update -y
    yum install -y httpd
    systemctl start httpd
    systemctl enable httpd
    echo "Hello from $(hostname)" > /var/www/html/index.html

Frequently Asked Questions

How do I convert CloudFormation JSON to YAML?

Use cfn-flip CLI tool (pip install cfn-flip), our online converter, or rain fmt command. Example: cfn-flip template.json > template.yaml. All methods preserve CloudFormation intrinsic functions correctly.

Should I use JSON or YAML for CloudFormation?

YAML is recommended for CloudFormation templates because it supports comments, is more readable, and allows shorthand syntax (!Ref instead of Fn::Ref). AWS fully supports both formats.

Does AWS CloudFormation support both JSON and YAML?

Yes, AWS CloudFormation fully supports both JSON and YAML template formats. You can use either format when creating stacks via Console, CLI, or API. The functionality is identical.

What is cfn-flip?

cfn-flip is a Python CLI tool specifically designed for converting CloudFormation templates between JSON and YAML. It correctly handles intrinsic functions, maintains formatting, and is widely used in the AWS community.

Need to convert CloudFormation templates?

Use our free online converter for instant JSON ↔ YAML conversion.

Open Converter Tool →