It was written and produced by Christian "Bloodshy" Karlsson and Peter Thomas, with additional writing from Tove Lo and Sam Shrieve, and co-production from Svidden.

Less than a month later, Duff released a "Fan-Demanded" version video, which does not show the Tinder material and instead focuses more on Hilary and her choreographed dancing to the song.

[6] In late January, she travelled to Sweden, where she collaborated with Swedish singer Tove Lo and record producer Jason "Ginni" Gill.

"[8] The following day, she posted a one-minute long sneak peek of Younger on YouTube, which was accompanied by a preview of a new song called "Sparks".

[12] Writing for Entertainment Weekly, Madison Vain drew comparisons of the song to the work of American singer Britney Spears, specifically her 2004 single "Toxic", which was co-produced by Bloodshy.

[12][14] Her "light" and "sweet-sounding" vocals are surrounded by "high twinkles", which Vanessa Golembewski of Refinery29 called "bubble gum enough you want to listen to it, but not so saccharine you feel like you stole your little sister's Disney channel CD.

"[12][15] Writing for Ryan Seacrest's entertainment website, Marc Inocencio noted that instead of "crescendoing into a synth-heavy drop", the song "pulls back" with an "infectious whistle" in between choruses.

[14] Bradley Stern of Idolator wrote that unlike Duff's previous "folk-tinged" singles, "Chasing the Sun" and "All About You", "Sparks" marks the return to a "more familiar" dance-pop sound for the singer.

The writer found the whistle breakdown in the song to be "unstoppably catchy", and wondered if it could be the "infectious hit" that she needs to be "propelled back onto pop radio".