As you probably know ReDoc was developed by Rebilly which is a payment/subscription company. Their main product is an API and it has a lot of endpoints and advanced payloads. They struggled to keep their docs up to date and that’s why they adopted OpenAPI (Swagger back then).
A few weeks ago, we migrated three API definitions that I maintain and contribute to OpenAPI 3 from Swagger 2. It is relatively easy to transition from version 2 to 3. But just migrating the definition was one thing… being able to contribute to new API definitions was something else entirely. I found 3 new features immediately useful.
By the time ReDoc was released in 2015, I was more comfortable with the OpenAPI specification.
ReDoc was born out of frustration with rendering my OpenAPI definitions for API reference docs.