OpenAPI v4.0 (A.K.A "Project Moonwalk")

OpenAPI v4.0, also known as "Project Moonwalk", is set to be released in 2024 with a focus on making the next version of OpenAPI more approachable and less complex for both humans and computers to write and understand. The new structure aims to reduce nested structures to improve readability and editability. It will support APIs that have different responses based on query parameters, headers, and request bodies, as well as a broader range of URL design patterns by adopting the URI Template RFC. Ongoing discussions include replacing $ref with "imports", improving tags, removing discriminator, and enhancing links functionality.