The single entered at the top of the UK Singles Chart, where it remained for three weeks until it was knocked off the summit by "Fireflies" by Owl City. Internationally, the single also topped the charts in Australia, Israel and Switzerland and peaked within the top ten of the charts in many countries, including Finland, France and the United States. The combined figure of the official music video and prequel video on YouTube is about 119 million views.
Beluga Heights label-mates Sean Kingston, Jason Derülo, and Iyaz himself all co-wrote the song together, along with label owner J.R. Rotem and songwriting duo Planet VI (known as Rock City at the time). Rotem also produced the track and credits himself at the beginning of the song via his signature "J-J-J-J-J.R." sample. The remix version with Flo Rida however, says, "BELUGA HEIGHTS" like in Jason Derülo's second single, "In My Head". Also, this is the second song that Jason Derülo, Kingston, and Rotem have co-written together, the first being Derülo's own debut single, "Whatcha Say".
The official music video features Iyaz wearing headphones and listening to music on a beach. Other various scenes feature Iyaz singing with a background of the British Virgin Islands' flag, and partying on the beach during the night. The video was directed by Rock Jacobs. A prequel video was also filmed that features the full-length beach scenes with Iyaz and his love interest.
The song debuted in the UK at number one on 10 January 2010, selling over 106,000 copies in its first week, the highest sale for any new year release since Michelle McManus sold 118,000 copies of "All This Time" in the equivalent week in January 2004. It is also the first number-one single of the 2010s (not counting Lady Gaga's "Bad Romance" which also reached number-one in 2009). After two weeks at number one on the UK Singles Chart and six weeks at the top of the UK R&B Chart, "Replay" was succeeded by Owl City's "Fireflies" and Rihanna's "Rude Boy", respectively. It was the first song released in 2010 in the UK to be certified Gold with sales in excess of 400,000. In June 2010, it was announced that "Replay" was the third highest selling single of the year in the UK at that point.
In the US, "Replay" has sold over 4 million digital copies as of December 2012.