APIs.guru vs CDNJS

APIs.guru maintains the largest searchable directory of OpenAPI/Swagger definitions for public APIs, normalizing specs pulled from thousands of providers into one browsable catalogue. Its own machine-readable endpoint (api.apis.guru/v2) needs no key or account and returns the full listing plus individual OpenAPI documents as JSON or YAML. The project is open-source and entirely free, run as a community effort rather than a paid product.

cdnjs mirrors thousands of open-source JavaScript, CSS, and font libraries on Cloudflare's edge network, and its free `/libraries` and `/libraries/:library` endpoints expose the same catalogue as JSON — name, latest version, file list, SRI hashes, and linked GitHub metadata — backed by Algolia search. No key or signup is required for either the asset CDN or the metadata API, and responses cache for six hours server-side.