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AWS launches AWS Emulator, a free local copy of AWS APIs for testing

Amazon Web Services released AWS Emulator on November 11, 2026: an official program that serves AWS API endpoints on your own machine, so the AWS CLI, AWS SDKs and coding agents can run tests without calling AWS. You don’t need an AWS account, it has no service fee, and the source code is on GitHub under a CC0 license. For developers it means an official alternative to mocking AWS calls or keeping a paid test account around just for integration tests.

What’s new

  • A local AWS endpoint. According to the AWS News Blog announcement, the emulator serves HTTPS on 127.0.0.1:9297. You point the CLI or an SDK at it with environment variables such as AWS_ENDPOINT_URL=https://127.0.0.1:9297, and your code doesn’t change.
  • Broad coverage. It supports the APIs of AWS services that have a model in AWS’s public API models repository. In a guest post on Werner Vogels’ blog, Swami Sivasubramanian writes that it was built from more than 400 API models and covers more than 200 services.
  • Resources persist while it runs. The user guide shows an S3 bucket created with aws s3api create-bucket showing up again in list-buckets, and a DynamoDB CreateTable call with a two-character name failing with the same ValidationException that AWS returns.
  • Three ways to run it. On Linux you install an RPM or Debian package for x86_64 or aarch64. On macOS and Windows you run it in Docker, from an image you build with the project’s Dockerfile (no prebuilt image is published). Tests written with the AWS SDK for Rust can use an embedded mode through the aws-emulator-embedded crate.
  • An agent skill. The GitHub repository says coding agents can install an aws-emulator skill with aws agent-toolkit add-skill, which needs AWS CLI 2.35.0 or later. The skill installs, starts and connects the emulator and checks whether your project works on it.
  • Price and license. AWS says there is no additional fee; you pay only for what you later deploy on AWS. The repository is CC0-1.0, with vendored code under Apache 2.0.

Built by agents

The emulator is written in Rust, and Sivasubramanian says all of its code was written and tested by AI agents. The project started with Amazon SQS, and he says a single prompt produced a passable first SQS emulator in about 15 minutes. Agents first adjust each fidelity test until it passes against real AWS, then build the emulator until it passes the same test. Changes go through a merge gate that includes automated security reviews. Simon Willison noted that the repository logged 29,684 commits in its first three weeks.

What it means for developers

The obvious use is integration tests in CI: create buckets, queues and tables against the emulator, run your suite, and throw the state away. The emulator keeps everything in memory and deletes it when it stops, and AWS suggests starting it for each test run or setting --idle-timeout.

On a Linux machine, the announcement shows this install:

PKG=https://downloads.aws.com/aws-emulator/packages/aws-emulator/LTS/latest
sudo dnf install -y $PKG/aws-emulator-x86_64.rpm
aws-emulator -v

Then run aws-emulator and set the endpoint variables. Some SDKs, such as the AWS SDK for Java, may need a trust store setting for the emulator’s certificate.

Know the limits before you rely on it:

  • No real IAM. It doesn’t evaluate IAM or resource-based policies the way AWS does, so a request AWS would deny can succeed locally. AWS says not to use it to test security.
  • One account, one Region. It acts as a single account (000000000000) and doesn’t separate resources by Region or account. Run one emulator per Region, each on its own port, if you need more.
  • Fidelity varies. Operations it doesn’t implement return HTTP 501. Each release publishes per-service fidelity scores on the releases page, and the tests are public in the aws-emulator-evaluation-suite repository. Behavior is checked against us-west-2 only, apart from global services.
  • Telemetry. It sends anonymous usage and error data by default, which you can turn off. AWS says it never sends your requests, responses or resource data.
  • Not for production or load tests. AWS hasn’t tested it for long-running use.

How it compares

Until now, teams that wanted to test against AWS without an account mocked SDK calls or used emulators from outside AWS. AWS Emulator is AWS’s own, built from the API models AWS publishes for its services and measured with public tests that are first checked against real AWS. Its gaps are documented in the open, including a things-that-do-not-work folder in the repository. Giving coding agents a safe place to run is a wider trend: NVIDIA recently donated its OpenShell agent sandbox to the CNCF, a runtime that sandboxes what AI agents can do.

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