Speaking with Pitchfork, Bjork said the track is an extension to a song off 2001's Vespertine: "Losss" is very much a continuation of 'Pagan Poetry,'" she said, "a certain sort of girl goth music."
"Losss" was co-produced by Texas-based producer Rabit. Speaking in Dazed's Autumn 2017 issue, Rabit said:
"The song that we made is pure feeling. It's my first outside production work - it's important that it means something. Thoughts and ideas have wings; we talked about this a lot throughout the process. How force of will is the ultimate force—our ability to choose. I think that the world needs a reminder of that right now. That's what the song is to me, and why it's so necessary."
Designed for the multiple screen viewing of Bjork's Cornucopia theatrical live show, the song's haunting music video features two creatures who take on a variety of different appearances. The clip was directed by Tobias Gremmler, who also had a role in bringing the Cornucopia stage production to life. The Icelandic singer said:
"We based the visuals on the conversations between our inner optimist and pessimist, when I recorded this I tried to sing in a deeper tone for one of them in the left speaker and a higher optimist in the right. And if you listen on headphones it will match the imagery."