Swift wrote “Castles Crumbling” around 2010 for her third studio album, Speak Now. Since then, fans gained knowledge of the song, but no part of it was actually ever heard until it was released as a From The Vault track on Speak Now (Taylor’s Version) on July 7th, 2023, featuring Taylor’s long-time friend, Hayley Williams.

In June 2023, a fan gifted Hayley with a bracelet themed after Speak Now, fact to which she said that was “coming at a very interesting time.” Her reaction brought fans to speculate about her appearence on the album, which was later confirmed when Swift posted its tracklist. While announcing it, Taylor mentioned that Hayley’s band, Paramore, was a huge influence to her around the time that she wrote Speak Now.

Although “Castles Crumbling” marks their first collaboration, Hayley had already been a guest star during Swift’s 2011 Speak Now Tour, and had also made an appearence in the music video for her 2015 single, “Bad Blood.” Hayley is also heavily rumoured to have been the inspiration behind the song “Speak Now.”

Lastly, two days before the song came out, Swift revealed on Twitter that Paramore would be an opening act for several of Taylor’s The Eras Tour dates in 2024.