API Simulator for Easy and Realistic API Simulations

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Applications Heavily Depend on APIs

It is common for an application to depend on the APIs of a dozen or more other applications and components.

These direct dependencies in turn have their own API dependencies, which may depend on even more APIs and so on...

api dependencies diagram

Problems with API Dependencies Hinder Testing and Development

unavailable api dependencies

Testing and development come to a halt when any one of the direct and transitive API dependencies is needed but unavailable.

Development of API Clients can be at standstill waiting for the delivery of new APIs.

External APIs charge pay-per-transaction fees even in non-production environments.

Often times API dependencies enforce rate limiting making performance testing impossible.

The Solution? API Simulations!

API Simulations imitate real APIs or APIs not built yet

API Simulations mimic the direct dependencies.

An API Simulation behaves and outputs static and dynamic data if it was "the real deal".

API Simulations are always available and with the right test data.

api simulations diagram

News and Announcements

API Simulator 1.10 is GA!

March 19, 2022

We are excited to announce the release of API Simulator version 1.10! mTLS (aka mutual TLS, two-way TLS, two-way SSL) is now supported to optionally require client authentication during the TLS/SSL handshake. Read more…

API Simulator 1.9 Release

April 19, 2021

We are excited to release API Simulator version 1.9! Stateful API Simulations just got better - all dynamic and without data preconfiguration. Read more…

API Simulator 1.8 Release

December 28, 2020

It is here: API Simulator version 1.8 is available for download! New features (who said Admin APIs?) and internal improvements make API Simulator leaner and meaner tool for your toolbox. Read more…


We invite you to learn more about API Simulator, download it, and run the examples. Why not even create API simulations to help your own testing and development?

Let us know what you think at [feedback at APISimulator.com]. Many thanks for your interest and support!

Happy API Simulating!