Format version
The AWSTemplateFormatVersion section (optional) identifies the capabilities
of the template. The latest template format version is
2010-09-09 and is currently the only valid value.
Note
The template format version isn't the same as the API or WSDL version. The template format version can change independently of the API and WSDL versions.
The value for the template format version declaration must be a literal string. You can't use a parameter or function to specify the template format version. If you don't specify a value, Amazon CloudFormation assumes the latest template format version. The following snippet is an example of a valid template format version declaration:
JSON
"AWSTemplateFormatVersion" : "2010-09-09"
YAML
AWSTemplateFormatVersion: "2010-09-09"