It uses Reddit's API, Algolia's HN API, and the Google News Api. Any of these services can be toggled individually in settings.

[0] - Reddit - https://github.com/reddit/reddit/wiki/API [1] - HN - https://hn.algolia.com/api [2] - https://developers.google.com/news-search/v1/devguide#gettin...

Also, it can be set to search a-la-carte by toggling Research Mode.