Critical response Alexis Petridis from
The Guardian praised the song, explaining, "Opener Under the Sun offers a weird and hugely enjoyable cocktail of tinny synthesiser, vast
Chemical Brothers-style breakbeat and football-terrace backing vocals".
Entertainment Wise also gave praise to the song, calling it "exceptional" along with album track "All Is Fair". Al Fox wrote for
BBC Music that "the casual, high-spirited Under the Sun boasts a playful, summery, arguably alternative trait." Laura Hills wrote a positive review for
MSN Music, calling it "a perfectly acceptable track full of bounce, upbeat vocals and what some may say are obvious references to ex-husband
Ashley Cole." Laurence Green from
musicOMH analysed that "Under the Sun serves as a thrillingly carefree album opener, all jaunty piano riffs and frat party chants. As one of Cole’s own co-writes, it’s hard not to read into the flippant breeziness of lyrics like "I got paid today, is this really my life, now that I’m over you... I can finally feel alive". In interviews, she might pointedly distance herself from any deeper meaning to the words, but truth be told, it's the way lines like these resonate so closely to Cole's own life that bolsters the album's cohesiveness and marks it out as a body of work that sounds fundamentally like ‘her’." Lewis Corner of
Digital Spy agreed, writing, "Cheryl may refuse to admit that her tracks are autobiographical, but when the credits list her as the primary songwriter, it's hard to ignore the song's potential to be a two-fingered salute to those who have attempted to sway her – and more power to her for it." Kim Taylor Bennet from
Time Out London called it a "
Lily Allen-lite, cheapened instantly to a Magaluf anthem by an inexplicable football chant refrain."
Chart performance "Under the Sun" debuted on the
UK Singles Chart at number 57, on 11 August 2012. Later, the song jumped to number 36, while on the third week, it climbed to number 26. ==Music video==