Instant live API mocks. Run standalone or inside your tests.

Imposter is a system that runs live, interactive mocks in place of real systems. Turn an OpenAPI file, WSDL file or any REST endpoint into a mock API for dev or QA. Run standalone mock servers, or embed mocks within your .

Made For Developers

From Web Developers to API Developers
Quick and Simple
Turn an OpenAPI file or WSDL file into a live mock with a single command. Call the mock from tests or run a standalone server.
Runs Everywhere
Run standalone mock servers with Docker or Lambda. Embed mocks within your tests with JUnit/JVM or Jest/Node.js.
Script dynamic responses with JavaScript or Groovy/Java. Advanced users can write plugins in any JVM language.
Fully Documented
Lots of samples, feature documentation and blog posts to get you started quickly.

How Does It Work

You're only a few simple steps away

Get started with a simple brew install command, or use our Node.js package or the Docker container to embed within your workflow.


Set up your static or dynamic responses. Choose from YAML/JSON or full customisation with scripts.


Start with a simple imposter up command, or run your Jest tests with npm test, or start the Docker container.

Seamless Integrations

Works great with major ecosystems

Get Started in No Time

Imposter makes it super easy to take control of your dependencies, so you can focus on delivering high quality software to your users.