AWS Releases Free Emulator for Developers to Test Cloud Apps Locally

Amazon Web Services (AWS) made AWS Emulator generally available Nov. 11, giving developers a free local way to test software that calls AWS APIs before deploying it to the cloud.

Developers can direct requests from the AWS Command Line Interface (CLI), software development kits (SDKs) and coding agents to a local endpoint on a computer, development server or continuous-integration (CI) environment. Local tests do not require an AWS account or cloud deployment, making the emulator an option for checking AWS-dependent software during development.

Autonomous AI agents wrote and maintain the emulator. They generate tests from API models, run them against AWS and use failures to identify gaps. Matthew Goldberg, an AWS senior principal engineer, said, “Our team hasn’t written or reviewed any of the code.”

For operations it supports, the emulator aims to return the same results for valid requests and the same errors for invalid ones as AWS. Unsupported operations return HTTP 501, or “Not Implemented.” AWS publishes fidelity tests and scores by service with each release, giving developers service-level results rather than one overall compatibility score.

AWS charges no separate fee for the emulator. Users pay for AWS resources when they deploy applications to the cloud. The source code is released under the CC0 1.0 Universal public-domain dedication, except for code in the vendor/ directory, which uses the Apache License 2.0.

The emulator is intended for development and testing, not production use or security testing. Its identity and access management (IAM) and resource-based policy checks differ from AWS’s, so a request AWS would reject could succeed in the emulator. State is held in memory and is lost when the program stops, while usage telemetry is enabled by default and can be turned off.