Because features and changes can introduce incompatible API changes, all Amazon EC2 API updates are versioned. By including a version in the request, clients receive responses they can process.

Each API revision is assigned a version in date form (the current API version is 2009-10-31). This version is included in the request as part of the document namespace when using our SOAP API and as a Version parameter when using our Query API. The response that Amazon EC2 returns honors the version included in the request.

SOAP clients that retrieve the Amazon EC2 WSDL at runtime and generate their requests dynamically using that WSDL should reference the WSDL for the version of the API that the client was developed against. This ensures that the client software continues to work even if backward incompatible API changes are introduced. The WSDL for each supported API version is available from the following URI:

http://ec2.amazonaws.com/doc/<api-version>/AmazonEC2.wsdl

The WSDL for latest version of our API is available from the following URI:

http://ec2.amazonaws.com/doc/2009-10-31/AmazonEC2.wsdl

	Note
	The WSDL should be treated as a moving target as it will always map to the latest release of the Amazon EC2 SOAP API. If your software depends on retrieving the WSDL at runtime, we strongly recommend you reference the specific version of the WSDL you are developing against.