APIs.guru vs Wandbox

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.

Wandbox is a free "social compilation service" built by melpon and kikairoya, offering 175 compiler configurations across 35 languages — from mainstream C++, Python, Rust, and Go to niche picks like Lazy K and Pony — including nightly HEAD builds of GCC and Clang. Its REST API needs no key: POST source code, a compiler ID, and options to /api/compile.json (or the /ndjson variant for streamed output) and get back compile/runtime output plus a permanent shareable permalink, while /api/list.json enumerates every compiler and its supported switches. The project was rewritten in 2024–2026 from a legacy Ruby backend to Rust (feline) and Remix (canine), which is why the old kennel2/API.rst docs path 404s — the live API endpoints themselves are unchanged.