AWS has released a free emulator that runs locally on a PC and offers APIs for parts of its cloud, allowing developers to test their software without connecting to the AWS cloud. The tool, called "AWS Emulator," is designed for development, testing, and CI environments.
Built in Rust, the emulator offers the APIs of AWS services that have an API model in the AWS API models repository on GitHub, which The Register reports contains over 1,300 items. AWS senior specialist solutions architect Daniel Abib said the choice of Rust helps ensure the tool “stays light on CPU and memory on a laptop.” The emulator does not replicate the entire AWS cloud. “It doesn't evaluate IAM policies the way AWS does, and each emulator acts as a single account, with no cross-account or cross-Region behavior,” Abib wrote. AWS publishes “fidelity scores” detailing how closely the emulator works with different services; Amazon tries to achieve full fidelity, so the emulator produces the same results as AWS for valid API calls and the same errors for invalid ones.
Developers can also direct AI coding agents to the emulator. AWS advises using the aws-emulator skill for this purpose, which checks a project's dependencies against the emulator's fidelity tests and scores. According to AWS documentation, the skill "tells you which parts of your project you can rely on the emulator for, and which ones might behave differently from AWS."
Installation is available via RPM or Debian package; Mac and PC users need to run Docker and an image of the Emulator. Abib explained that once started, the emulator generates its own credentials and configuration. “You set environment variables so the AWS SDK talks to your laptop instead of AWS, and your application code stays unchanged,” he instructed. Existing tests and scripts should continue working as before, without requiring a cloud deployment.
The move appears intended to encourage more use of AWS cloud by making it easier for developers to test locally.
Analysis
Why This Matters
- Developers can test AWS-dependent code locally without network calls, speeding up development and reducing costs from cloud usage during testing.
- The emulator lowers the barrier for using AWS by enabling offline testing and integration into continuous integration pipelines.
- Could increase confidence in deploying to AWS, potentially boosting platform adoption.
Background
Cloud services are typically accessed over the internet, requiring connectivity for testing. Local emulation is a common software development practice that allows developers to test without network dependencies. AWS has now released an official emulator to serve this need directly.
What to Watch
- The fidelity scores for popular services like DynamoDB and S3 will indicate how practical the emulator is for real development work.
- Community adoption and whether AWS expands the emulator to cover more of its wide range of services.
- Integration of the emulator into CI/CD pipelines as a standard step.
Checked
12 claims in this story checked against 1 source: 12 supported.
Show each claim
- SupportedAWS has released a local emulator for cloud API testing.www.theregister.com - Articles: “AWS has released an emulator that kind-of-almost lets you use its cloud on a PC.”
- SupportedThe emulator lets developers test applications on their own machines without calling AWS.www.theregister.com - Articles: ““You use it to test your software without calling AWS, on your own machine, on a development server, or in continuous integration (CI),” the repo explains.”
- SupportedThe emulator is free to use.www.theregister.com - Articles: “Because those tests never touch the AWS cloud, the tool is free to use.”
- SupportedThe emulator is intended for development, testing and CI environments.www.theregister.com - Articles: ““You use it to test your software without calling AWS, on your own machine, on a development server, or in continuous integration (CI),” the repo explains.”
- SupportedAWS wrote the emulator in Rust, and Daniel Abib said Rust helps it “stay light on CPU and memory on a laptop.”www.theregister.com - Articles: “AWS wrote the emulator in Rust, a choice that senior specialist solutions architect Daniel Abib wrote helps to ensure the tool “stays light on CPU and memory on a laptop.””
- SupportedThe emulator offers APIs for AWS services with an API model in the AWS API models repository, which The Register found contained over 1,300 items.www.theregister.com - Articles: “Abib said it supports the APIs of AWS services that have an API model in the AWS API models repository on GitHub. The Register found over 1,300 items on that page.”
- SupportedAbib wrote that the emulator does not evaluate IAM policies as AWS does and that each emulator is a single account with no cross-account or cross-Region behavior.www.theregister.com - Articles: ““It doesn’t evaluate IAM [Identity and Access Management] policies the way AWS does, and each emulator acts as a single account, with no cross-account or cross-Region behavior,” Abib wrote”
- SupportedAWS publishes fidelity scores for how closely the emulator works with different services, and aims for matching AWS results for valid API calls and errors for invalid ones.www.theregister.com - Articles: “AWS publishes “fidelity scores” that detail how closely the emulator works on different AWS services. Amazon tries to achieve full fidelity, so the emulator produces the same results as AWS for valid API calls, and the same errors for invalid ones.”
- SupportedAWS advises using the aws-emulator skill for AI coding agents, which checks project dependencies against emulator fidelity tests and scores.www.theregister.com - Articles: “AWS advises the easiest way to check if a project will work with the tool is to use the aws-emulator skill for AI coding agents. “With the skill, your agent finds the AWS operations and resources that your project depends on. It checks them against the fidelity tests and fidelity scores for the emulator.””
- SupportedAWS documentation says the skill “tells you which parts of your project you can rely on the emulator for, and which ones might behave differently from AWS.”www.theregister.com - Articles: ““It then tells you which parts of your project you can rely on the emulator for, and which ones might behave differently from AWS,” according to AWS documentation.”
- SupportedThe emulator is available as an RPM or Debian package, while Mac and PC users need Docker and an image of the Emulator.www.theregister.com - Articles: “AWS has made the emulator available as an RPM or Debian package. Mac and PC users will need to run Docker and an image of the Emulator.”
- SupportedAbib said users can set environment variables so the AWS SDK talks to their laptop instead of AWS while application code stays unchanged.www.theregister.com - Articles: ““You set environment variables so the AWS SDK talks to your laptop instead of AWS, and your application code stays unchanged.””
