According to Swift, “Fortnight” explores “fatalism, longing, pining away, lost dreams.” The single broke the record for the highest single-day streams on the streaming platform Spotify. In the United States, the song debuted atop the Billboard Hot 100, marking Swift’s twelfth and Malone’s fifth number-one song. “Fortnight” earned Swift her fifth number-one single on the Billboard Global 200 chart and peaked atop the charts in Australia, Canada, Malaysia, New Zealand, the Philippines, Singapore, the United Arab Emirates, and the United Kingdom. The vocal chemistry between Swift and Malone in “Fortnight” was the subject of critical praise, but some critics found the production weaker compared to Swift’s other singles. At the forthcoming 67th Annual Grammy Awards, “Fortnight” has been nominated for Song of the Year and Record of the Year.

A music video for “Fortnight”, directed by Swift, accompanied the song’s release. It stars Swift and Malone as lovers, and the American actors Ethan Hawke and Josh Charles as mad scientists experimenting on Swift. Employing a black-and-white aesthetic by Mexican cinematographer Rodrigo Prieto, the video features clips of a gothic Swift in a psychiatric hospital, and a Victorian Swift romancing with Malone in an office. “Fortnight” garnered nine nominations at the 2024 MTV Video Music Awards, winning five, including Video of the Year, and won Best Video at the 2024 MTV Europe Music Awards as well. It has been nominated for Best Music Video at the 67th Annual Grammy Awards and the 32nd Camerimage festival.