This topic describes how to initiate API requests over HTTP. This topic is intended for users who initiate HTTP or HTTPS GET requests by calling API operations.


You can create only a specified number and specified types of dedicated hosts. For more information, see Limits.

If API descriptions, optional parameter values, or available specifications conflict with the resource or specification limits described in the Limits topic, the limits prevails.

Developer options

You can call an API operation by using the following methods:
  • (Recommended) Programming language-specific SDKs for the API.
  • Alibaba Cloud OpenAPI Explorer
  • Configure Alibaba Cloud CLI. For more information, see What is Alibaba Cloud CLI?
  • URL-based API requests.
    Note To send URL requests to the API, you must complete the authentication process and prepare the URL for every request. For more information, see Request method.

You can skip the authentication process by using the SDK, CLI, or API Explorer to call API operations.

Note When you call API operations by using Alibaba Cloud CLI or SDKs, you must delete periods (.) from some request parameters before you use the parameters. For example, use SystemDiskCategory instead of SystemDisk.Category as a request parameter.

Request syntax

The request URL consists of different parameters and has a fixed syntax. The URL contains common parameters, your signature, and operation-specific parameters. Sample URL requests are provided in every API reference topic. However, these topics do not describe how to encode URLs. You must encode the related URL before you make a request. For more information, see Request method, Common parameters, and Signature method.

The system returns the request result based on your signature verification. Response parameters are displayed if the call succeeds, and an error message appears if the call fails. You can troubleshoot issues based on the common error codes and operation-specific error codes.

DDH shares the same endpoint with Elastic Compute Service (ECS). For more information, see Request syntax.