Cataas vs RandomDuck

Cataas ("Cat as a Service") is a free, open-source REST API that returns random cat images and animated GIFs, filterable by tag, with options to overlay custom text or crop a specific position. A JSON mode (?json=true) returns the image's metadata — id, tags, and direct URL — instead of the binary file itself. It's maintained on GitHub under the cataas org with no signup or pricing tier; a Donate link is the site's only monetization.

Random-d.uk's /random endpoint returns a JSON object linking to a random duck photo or GIF, with a type query parameter to request JPG or GIF specifically. A companion /randomimg endpoint serves the image file directly instead of the JSON wrapper, and the service also accepts community-submitted duck photos.