AdoptAPet vs HTTP Dog

AdoptAPet's free Pet List API lets a registered shelter or rescue pull its own current adoptable-pet listings — name, photo, breed, and a link back to the pet's page — for display on its own website; it doesn't cover other shelters' animals or expose network-wide search. Access needs a per-shelter API key passed as a key query parameter to endpoints like api.adoptapet.com/search/pets_at_shelter, confirmed live by a real GET that returns a JSON invalid_key error rather than a redirect or outage, with a separate OPTIONS preflight and that same GET both echoing access-control-allow-origin: * back for a test Origin header. The official documentation page now sits behind a shelter-account login (a live probe returns 401 with a Basic-auth challenge, a change from when it was openly readable), but the API endpoint itself remains fully live and free, returning JSON or XML depending on the output parameter.

http.dog serves a themed dog photo for most standard HTTP status codes (e.g. GET /200, /404, /451), following the same status-code-as-image idea as http.cat. A .json variant returns direct links to the same image in JPEG, WebP, AVIF, and JXL instead of the image itself. It's a static Cloudflare-fronted site with no server-side application logic, so there's no API key, authentication, or rate limit of any kind.