Swagger is an open source platform that provides a variety of tools for developers to assist them in designing, building, documenting, and consuming RESTful web services. Although Swagger is generally known for its user interface tools, it also provides the user with other tools, such as automation and test cases.

At first, the popularity of the Swagger API was limited to the reach of small-scale organizations and individual developers. Most of the time, mechanisms that support machine readability are not available with RESTful APIs, but the Swagger API provided an easy and simple way of doing so. However, soon enough, with the help of an open source license from Apache 2.0, products and online services started offering Swagger as a part of their toolkit. This soon led to global companies, such as Apigee, Intuit, Microsoft, and IBM, to start endorsing the Swagger project publicly.

Let's see the usage of the Swagger for the REST APIs in the next section.