Prism is a set of packages for API mocking with OpenAPI v2 (formerly known as Swagger Specification) and OpenAPI v3.

For example, given an API specification you can spin up a mock HTTP server and respond realistically based on your requests

Note: This branch refers to Prism 3.x, which is the current version most likely you will use. If you're looking for the 2.x version, look at the 2.x branch

npm install -g @stoplight/prism-cli

# OR

yarn global add @stoplight/prism-cli

For more installation options, see Getting Started > Installation

After installation take a look at our getting started documentation.

• Server Validation
• Content Negotiation
• Security Validation
• Custom Mocking
• Validation Proxy
• Recording / "Learning" mode to create spec files
• Data Persistence (allow Prism act like a sandbox)

Cannot access mock server when using docker?

Prism uses localhost by default, which usually means 127.0.0.1. When using docker the mock server will be unreachable outside of the container unless you run the mock command with -h 0.0.0.0.

Why am I getting 404 errors when I include my basePath?

OpenAPI v2.0 had a concept called "basePath", which was essentially part of the HTTP path the stuff after host name and protocol, and before query string. Unlike the paths in your paths object, this basePath was applied to every single URL, so Prism v2.x used to do the same. In OpenAPI v3.0 they merged the basePath concept in with the server.url, and Prism v3 has done the same.

We treat OAS2 host + basePath the same as OAS3 server.url, so we do not require them to go in the URL. If you have a base path of api/v1 and your path is defined as hello, then a request to http://localhost:4010/hello would work, but http://localhost:4010/api/v1/hello will fail. This confuses some, but the other way was confusing to others. Check the default output of Prism CLI to see what URLs you have available.

If you are interested in contributing to Prism itself, check out our contributing docs ⇗ and code of conduct ⇗ to get started.

In case you're interested in all logical decision we make to figure out the best HTTP response to the specific request, you can consult our diagram