Swagger Contracts

Unlike SOAP APIs, which is effectively considered the predecessor of REST APIs, there was no solution for built-in documentation and schema validation from the beginning. Therefore, there were a lot of proprietary approaches that sometimes worked better and sometimes worse.

OpenAPI

Swagger also emerged from such a solution-seeking approach, and is effectively a compilation of several open source ideas. The way of Swagger, especially the possibility to create client and server automatically based on a complete API documentation, helped to break through and finally ensured that today Swagger is developed as OpenAPI and is an official API standard since 2016.

The name Swagger has survived to this day, but only represents the tooling and no longer the API standard itself.