CloudFormation Template Anatomy

Every CloudFormation template follows a well-defined structure. Understanding the anatomy of a template is essential for writing, reading, and debugging infrastructure definitions. In this lesson we will examine each section of a template, what it does, and when to use it.

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The Six Sections of a CloudFormation Template

A CloudFormation YAML template can contain the following top-level sections:

AWSTemplateFormatVersion: '2010-09-09'
Description: A description of what this template does

Metadata:
  # Optional information about the template

Parameters:
  # Input values supplied at stack creation time

Mappings:
  # Static key-value lookup tables

Conditions:
  # Logic to control whether resources are created

Resources:
  # The AWS resources to create (REQUIRED)

Outputs:
  # Values to return after the stack is created

Only the Resources section is required. All other sections are optional, but most real-world templates use several of them.

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AWSTemplateFormatVersion

This declares the template format version. The only valid value is '2010-09-09', which has been the version since CloudFormation launched. You should always include it for clarity:

AWSTemplateFormatVersion: '2010-09-09'

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Description