The song debuted at number one on the UK Singles Chart. It also peaked at number three in the Republic of Ireland. It has sold over 560,000 copies in the United Kingdom as of August 2014, making it the band's best-selling song.
After finishing as runners-up to Alexandra Burke on the fifth series of The X Factor in December 2008, JLS signed a record deal with Epic Records. Epic managing director Nick Raphael said, "JLS are the best boy band to emerge from a TV talent show. The band already have an incredible fan base, and I look forward to launching their recording career."
"Beat Again" was unusual for being a debut single from reality show contestant in that was not a cover version, following in the footsteps of Girls Aloud, Shayne Ward and Leona Lewis. Instead, this song written especially for JLS by Wayne Hector and Steve Mac. The song was originally titled 'No Beat' and supposedly took only two hours to write. Mac himself had originally presented the song to Nick Raphael, JLS' A&R at Epic Records, as a potential single. "Beat Again" is written in the key of A-flat minor. Raphael had originally been looking for a ballad in the vein of Boyz II Men's "End of the Road" and had in fact already asked Mac for another "Flying Without Wings". However, according to co-writer Wayne Hector, Raphael's response upon hearing the new song was, "this is the single. I can feel it. It's fantastic." Raphael had supposedly originally intended "Everybody in Love" to be the lead single but changed his mind at the last minute.
To date, "Beat Again" has garnered mixed to positive reviews from music critics. Giving the single three stars, Alex Fletcher of Digital Spy noted that JLS "have at least broken with X Factor convention on their debut single". Fletcher also drew positive comparisons to work by American R&B artist Ne-Yo. However, the reviewer went on to say the single is "cheesier than a Jennifer Aniston rom-com". Another review, giving the single three stars out of five, said "Beat Again seems to lack originality". It was included on the Popjustice song of the day. The Daily Record wrote that the single had "the R&B electro sass of Justin Timberlake or Rihanna [and] will surprise many".
"Beat Again" made its chart debut on the Billboard Euro Digital Tracks chart at number 13, and on the Euro Digital Songs at number 19. The song debuted on the Irish Singles Chart at number four. The song debuted at number one on the UK Singles Chart. It sold 106,299 copies in its first week on sales, making it the second fastest-selling single of 2009, behind Dizzee Rascal's "Bonkers". "Beat" Again" has sold 560,000 copies in the UK as of 2014. The song was also released in the United States in July 2009, but failed to chart or garner commercial interest.
The music video was shot in May 2009 and released on 4 June 2009. It features various scenes of JLS dancing to the song in front of blue, red, yellow and green lights, all of which represent the different band members. The dance choreography involves moves revolving around heartbeats, alluding to the title "Beat Again".