"Happy" is a midtempo soul and neo soul song on which Williams's falsetto voice has been compared to Curtis Mayfield by critics. The song has been highly successful, peaking at No. 1 in the United States, United Kingdom, Canada, Ireland, New Zealand, and 19 other countries. It was the best-selling song of 2014 in the United States with 6.45 million copies sold for the year,[3] as well as in the United Kingdom with 1.5 million copies sold for the year.[4] It reached No. 1 in the UK on a record-setting three separate occasions and became the most downloaded song of all time in the UK in September 2014. It was nominated for an Academy Award for Best Original Song. A live rendition of the song won the Grammy Award for Best Pop Solo Performance at the 57th Annual Grammy Awards.