OpenAPI

OpenAPI deserves a catalog entry because it is not just background industry vocabulary. It is one of the central standards shaping how modern API tooling works across documentation, SDK generation, testing, mocking, and governance. The official OpenAPI Initiative publications site makes clear that it maintains the authoritative specification renderings and registries. That makes OpenAPI relevant not only as a concept, but as an actual foundational dependency in real API stacks.

Its pricing story is simple because OpenAPI is a standard, not a SaaS product. The specification is openly published by the OpenAPI Initiative, licensed under Apache 2.0 on the official publications site, and there is no subscription fee to adopt the spec itself. Teams still pay for the tools built around OpenAPI, but the standard is free. That is exactly how the entry should be framed editorially.