Amazon Elastic Compute Cloud
API Reference (API Version 2016-11-15)

Query Requests

Query requests are HTTP or HTTPS requests that use the HTTP verb GET or POST and a Query parameter named Action. For a list of Amazon EC2 API actions, see Actions.

Structure of a GET Request

The Amazon EC2 documentation presents the GET requests as URLs, which can be used directly in a browser.


Because the GET requests are URLs, you must URL encode the parameter values. In the Amazon EC2 documentation, we leave the example GET requests unencoded to make them easier to read.

The request consists of the following:

  • Endpoint: The URL that serves as the entry point for the web service.

  • Action: The action that you want to perform; for example, use RunInstances to launch an instance.

  • Parameters: Any parameters for the action; each parameter is separated by an ampersand (&).

  • Version: The API version to use.

  • Authorization parameters: The authorization parameters that AWS uses to ensure the validity and authenticity of the request. Amazon EC2 supports Signature Version 2 and Signature Version 4; for more information, see Signature Version 2 Signing Process and Signature Version 4 Signing Process in the Amazon Web Services General Reference.

The following optional parameters can be included in your request:

  • DryRun: Checks whether you have the required permissions for the action, without actually making the request. If you have the required permissions, the request returns DryRunOperation; otherwise, it returns UnauthorizedOperation.

  • SecurityToken: The temporary security token obtained through a call to AWS Security Token Service.

For more information about common parameters for API requests, see Common Query Parameters.

The following is an example request that launches instances:

Copy Content-type: application/json

To make these example requests even easier to read, AWS documentation may present them in the following format:

Copy &ImageId=ami-2bb65342 &MaxCount=3 &MinCount=1 &Placement.AvailabilityZone=us-east-1a &Monitoring.Enabled=true &Version=2016-11-15 &X-Amz-Algorithm=AWS4-HMAC-SHA256 &X-Amz-Credential=AKIAIOSFODNN7EXAMPLEus-east-1%2Fec2%2Faws4_request &X-Amz-Date=20130813T150206Z &X-Amz-SignedHeaders=content-type%3host%3x-amz-date &X-Amz-Signature=ced6826de92d2bdeed8f846f0bf508e8559e98e4b0194b84example54174deb456c Content-type: application/json

The first line specifies the endpoint of the request. After the endpoint is a question mark (?), which separates the endpoint from the parameters.

The Action parameter indicates the action to perform. For a complete list of actions, see Actions. The remaining lines specify additional parameters for the request.

In the example Query requests we present in the Amazon EC2 API documentation, we omit the headers, common required parameters, and authentication parameters to make it easier for you to focus on the parameters for the action. We replace them with the &AUTHPARAMS literal string to remind you that you must include these parameters in your request; for example:

Copy &ImageId=ami-2bb65342 &MaxCount=3 &MinCount=1 &Placement.AvailabilityZone=us-east-1a &Monitoring.Enabled=true &AUTHPARAMS


Before you specify your access key ID for the AWSAccessKeyId or Credential parameter, review and follow the guidance in Best Practices for Managing AWS Access Keys.


An endpoint is a URL that serves as an entry point for a web service. You can select a regional endpoint for Amazon EC2 when you make your requests to reduce latency. For more information about regions, see Regions and Availability Zones in the Amazon EC2 User Guide for Linux Instances. For information about the endpoints for Amazon EC2, see Regions and Endpoints in the Amazon Web Services General Reference.

If you specify the general endpoint,, we use the endpoint for us-east-1. To use a different region, specify its associated endpoint. For example, if you specify as the endpoint, we direct your request to the us-east-2 endpoint.

Query Parameters

Each Query request must include required common parameters to handle authentication and selection of an action.

Some operations take lists of parameters. These lists are specified using the param.n notation, where n is an integer starting from 1.

The following example adds multiple devices to a block device mapping using a list of BlockDeviceMapping parameters.

Copy &ImageId.1=ami-72aa081b ... &BlockDeviceMapping.1.DeviceName=/dev/sdj &BlockDeviceMapping.1.Ebs.NoDevice=true &BlockDeviceMapping.2.DeviceName=/dev/sdh &BlockDeviceMapping.2.Ebs.VolumeSize=300 &BlockDeviceMapping.3.DeviceName=/dev/sdc &BlockDeviceMapping.3.VirtualName=ephemeral1 &AUTHPARAMS

Query API Authentication

You can send Query requests over either the HTTP or HTTPS protocol.

Regardless of which protocol you use, you must include a signature in every Query request. Amazon EC2 supports Signature Version 2 and Signature Version 4. For more information, see Signature Version 2 Signing Process and Signature Version 4 Signing Process in the Amazon Web Services General Reference.

Signature Version 4 requests allow you specify all the authorization parameters in a single header, for example:

Content-Type: application/x-www-form-urlencoded; charset=UTF-8 X-Amz-Date: 20130813T150211Z Host: Authorization: AWS4-HMAC-SHA256 Credential=AKIDEXAMPLE/20130813/us-east-1/ec2/aws4_request, SignedHeaders=content-type;host;x-amz-date, Signature=ced6826de92d2bdeed8f846f0bf508e8559e98e4b0194b84example54174deb456c ImageId=ami-2bb65342 &MaxCount=3 &MinCount=1 &Monitoring.Enabled=true &Placement.AvailabilityZone=us-east-1a &Version=2016-11-15

Query Response Structures

In response to a Query request, the service returns an XML data structure that conforms to an XML schema defined for Amazon EC2. The structure of an XML response is specific to the associated request. In general, the response data types are named according to the operation performed and whether the data type is a container (can have children). Examples of containers include groupSet for security groups and keySet for key pairs (see the example that follows). Item elements are children of containers, and their contents vary according to the container's role.

Every successful response includes a request ID in a requestId element, and every unsuccessful response includes a request ID in a RequestID element. The value is a unique string that AWS assigns. If you ever have issues with a particular request, AWS will ask for the request ID to help troubleshoot the issue. The following shows an example response.

<DescribeKeyPairsResponse xmlns=""> <requestId>7a62c49f-347e-4fc4-9331-6e8eEXAMPLE</requestId> <keySet> <item> <keyName>gsg-keypair</keyName> <keyFingerprint> 00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00 </keyFingerprint> </item> </keySet> </DescribeKeyPairsResponse>