"Eilish and Finneas spent a week recording the song—“We just sat in his room dancing to it,” she recalled—and uploaded it to SoundCloud simply to have a shareable link for Eilish’s dance teacher. Then the blog Hillydilly picked it up, and that led to Beats 1 tastemaker Zane Lowe voicing his support—and the track went viral."

https://www.wmagazine.com/story/billie-eilish-new-ep