Simulate API conditions with Postman Simulator

With Postman Simulator, you group mocks into a single environment that stands in for the services your app depends on, such as a cart, a payment API, or a notification service. You or your coding agent can develop and test against the whole dependency set at once, whether locally, in CI, or from a deployed mock server. Each dependency can apply behaviors like latency, errors, and rate limits.

A simulation runs on your machine, so you can develop against your dependencies without sandbox accounts, credentials, or a shared environment. Because its mocks stand in for the real services, you can iterate without real side effects like charges or emails, and it stays reproducible because it behaves only the way you configured it.

Simulations are most useful when you want to see how your service responds when multiple dependencies fail at once. For example, you can combine a mock that simulates a slow auth service with one that returns errors from an inventory API, then observe how your service handles both together.

Create and run a simulation

A simulation groups one or more mocks so you can run them together. You choose which mocks to include, set how requests reach each one, and then run the simulation locally or deploy it as a mock server. You can edit the simulation at any time.

Learn how to create and run a simulation.

Apply scenarios and behaviors

For each mock in a simulation, select a scenario and, optionally, override its behaviors without changing the scenario itself. This lets you push a scenario further for a specific run, such as overriding a scenario’s 500 ms latency to 5000 ms for a load test while the original scenario stays unchanged.

Learn how to apply scenarios and behaviors.

Make calls to a simulation

Send requests to a running simulation and observe how each mock responds with its behaviors applied. How you reach a member depends on whether you route by URL path or header.

Learn how to make calls to a simulation.

View simulation logs and history

View a running simulation’s request logs, and review past runs in its run history.

Learn how to view simulation logs and history.