Nightcore refers to an edited version of a music track that increases the pitch and tempo of its source material.
The name is derived from the Norwegian musical duo Nightcore, who released pitch-shifted versions of trance and Eurodance songs. Nightcore is also almost always associated and accompanied with anime and otaku culture, with many YouTube thumbnails, and similar formats, of nightcore remixes containing anime characters and art.
Nightcore saw a general resurgence in popularity in the early 2020s due to TikTok, causing major recording labels to officially release sped-up versions of their songs.