a nightcore edit is a version of a music track that increases the pitch and speeds up its source material by approximately 35%. this gives an effect almost identical to playing a 33⅓-RPM vinyl record at 45 RPM. this 35% increase in RPM causes the note C4 to become slightly lower in pitch than the note F#4 (261.63 Hz becomes 353.19 Hz) which is an increase of approximately 5 and a half semitones. playing 33⅓-RPM vinyl trance records at 45RPM was common in the Happy Hardcore scene of the 90s and 2000s, which most likely inspired the genre.

the name is derived from the Norwegian musical duo "Nightcore", who released pitch-shifted versions of trance and Eurodance songs. nightcore is also commonly associated and accompanied with anime and otaku culture, with many YouTube thumbnails of nightcore remixes containing anime characters and art.