AWS Region - AWS SDKs and Tools
Compatibility with AWS SDKs

AWS Region

AWS Regions are an important concept to understand when working with AWS services.

With AWS Regions, you can access AWS services that physically reside in a specific geographic area. This can be useful to keep your data and applications running close to where you and your users will access them. Regions provide fault tolerance, stability, and resilience, and can also reduce latency. With Regions, you can create redundant resources that remain available and unaffected by a Regional outage.

Most AWS service requests are associated with a particular geographic region. The resources that you create in one Region do not exist in any other Region unless you explicitly use a replication feature offered by an AWS service. For example, Amazon S3 and Amazon EC2 support cross-Region replication. Some services, such as IAM, do not have Regional resources.

The AWS General Reference contains information on the following:

  • To understand the relationship between Regions and endpoints, and to view a list of existing Regional endpoints, see AWS service endpoints.

  • To view the current list of all supported Regions and endpoints for each AWS service, see Service endpoints and quotas.

Creating service clients

To programmatically access AWS services, SDKs use a client class/object for each AWS service. If your application needs to access Amazon EC2, for example, your application would create an Amazon EC2 client object to interface with that service.

If no Region is explicitly specified for the client in the code itself, the client defaults to using the Region that is set through the following region setting. However, the active Region for a client can be explicitly set for any individual client object. Setting the Region in this way takes precedence over any global setting for that particular service client. The alternative Region is specified during instantiation of that client, specific to your SDK (check your specific SDK Guide or your SDK's code base).

Configure this functionality by using the following:

region - shared AWS config file setting
AWS_REGION - environment variable
aws.region - JVM system property: Java/Kotlin only

Specifies the default AWS Region to use for AWS requests. This Region is used for SDK service requests that aren't provided with a specific Region to use.

Default value: None. You must specify this value explicitly.

Valid values:

  • Any of the Region codes available for the chosen service, as listed in AWS service endpoints in the AWS General Reference. For example, the value us-east-1 sets the endpoint to the AWS Region US East (N. Virginia).

  • aws-global specifies the global endpoint for services that support a separate global endpoint in addition to Regional endpoints, such as AWS Security Token Service (AWS STS) and Amazon Simple Storage Service (Amazon S3).

Example of setting this value in the config file:

[default]
region = us-west-2

Linux/macOS example of setting environment variables via command line:

export AWS_REGION=us-west-2

Windows example of setting environment variables via command line:

setx AWS_REGION us-west-2

Most SDKs have a "configuration" object that is available for setting the default Region from within the application code. For details, see your specific AWS SDK developer guide.

Compatibility with AWS SDKs

The following SDKs support the features and settings described in this topic. Any partial exceptions are noted. Any JVM system property settings are supported by the AWS SDK for Java and the AWS SDK for Kotlin only.

SDK Supported Notes or more information
AWS CLI v2 Yes AWS CLI v2 uses any value in AWS_REGION before any value in AWS_DEFAULT_REGION (both variables are checked).
AWS CLI v1 Yes AWS CLI v1 uses environment variable named AWS_DEFAULT_REGION for this purpose.
SDK for C++ Yes
SDK for Go V2 (1.x) Yes
SDK for Go 1.x (V1) Yes To use shared config file settings, you must turn on loading from the config file; see Sessions.
SDK for Java 2.x Yes
SDK for Java 1.x Yes
SDK for JavaScript 3.x Yes
SDK for JavaScript 2.x Yes
SDK for Kotlin Yes
SDK for .NET 3.x Yes
SDK for PHP 3.x Yes
SDK for Python (Boto3) Yes This SDK uses environment variable named AWS_DEFAULT_REGION for this purpose.
SDK for Ruby 3.x Yes
SDK for Rust Yes
SDK for Swift Yes
Tools for PowerShell Yes