[3] An avant-pop album with a horror-like atmosphere and whispery vocals,[4][5][6] it debuted atop record charts in various countries and brought Eilish to mainstream fame.

[11] Her brother Finneas O'Connell confirmed this during a March 2020 interview, stating that it would be "pretty pure in its intention" and something that they would appreciate making and performing live.

The song was first used in the 2021 documentary film Billie Eilish: The World's a Little Blurry, revealing the lyrics "when I'm away from you, I'm happier than ever, wish I could explain it better.

She explained that the recording process felt like finding the best way to tell a person something she wished to tell them for a while: "You don't really know what you want to say or how to say it—and then maybe you have a conversation with somebody else, or you think a little bit about it, and you figure out what it is..."[20]"Happier Than Ever" is a sentimental power ballad.

[37][38] In an act of catharsis, Eilish continues the song by yelling some of its lyrics to express her pain,[39][40] with a multitracking technique applied to her voice.

[41] Multiple critics noted that Eilish's screams and Finneas's rock-infused production marked a significant departure from both of their previous musical styles.

[54] On April 26, she released a 15-second long snippet of "Happier Than Ever" on her Instagram account, featuring visuals of her sitting in a chair with her back to the camera.

[49][61] Critics who dubbed the song a highlight included Consequence's Mary Siroky,[62] Pitchfork's Quinn Moreland,[63] and Complex's Jessica McKinney.

[64] Jason Lipshutz, a staff editor for Billboard, thought that it "best captures the essence of the album" due to demonstrating Eilish's songwriting and vocal talents, which he believed was a defiance of traditional expectations from pop music.

[65] In an article for NME, El Hunt argued that Eilish's performance in the song offered powerful emotional impact and proved that her voice had improved throughout the years.

[40] Evaluating the album for Stereogum, Tom Breihan opined that "Happier Than Ever" provided it with the "only real moment of greatness, and he lamented that the rest of its tracks were not as vocally loud and cathartic.

[69] Zoladz thought the song is the album's "most exhilarating moment" and a "disarmingly earnest torrent of bottled-up grievances", a full display of Eilish's versatility.

[70][71] The former magazine's Brittany Spanos stated that the song is "pure angst and a departure [from her] usually cool-headed" demeanor, and likened its beginning to a lamb and its outro to "a whole pack of lions".

[93] It peaked at number four on the UK Singles Chart in the United Kingdom,[94] and earned a Platinum certification from the British Phonographic Industry in March 2022.

[122] Ellie Robinson of NME praised the video as a "poignant film clip", and Billboard's Hannah Dailey opined its transition encapsulates breaking in the "facade of serenity" and that "instead of cowering there, she embraces the wrath of the storm".

Eilish sang in front of clouds and flashing lights that gave the impression of a storm, joined by a drummer and Finneas on the guitar.

on top of The Hollywood Roosevelt Hotel on October 14,[126][127] and at Saturday Night Live on December 11, where they performed it alongside "Male Fantasy" (2021).

[129][130] The following month, she visited the World Cafe radio program to sing "Happier Than Ever" alongside three other tracks from the album: "Billie Bossa Nova", "Goldwing", and "Halley's Comet".

[131] Eilish included a performance of the song in her concert film Happier Than Ever: A Love Letter to Los Angeles, released to Disney+ on September 3, 2021.

[132][133] She added it as the final song of the set list of a 2022–2023 world tour, which started on February 3, 2022, in New Orleans, Louisiana, at Smoothie King Center and finished on September 30, 2022, at Perth Arena, in support of the album,[134] and sang the song as a closing number on April 16 for that year's Coachella festival, amid gusts of wind from a dust storm.

[140] She began by singing inside an upside-down model of a house, donning a shirt which paid tribute to Taylor Hawkins, who had died earlier in the week.

Eilish climbed atop the roof and banged her head while Finneas played the guitar; the performance concluded with thunder and lightning striking as rain poured down the stage.

[143] On July 30, 2022, in celebration of the album's one-year anniversary, Eilish and Finneas headed for the Amoeba Music record store in Hollywood to perform "Happier Than Ever", along with three other songs.

[145][146][147] Canadian singer Shawn Mendes and Japanese-British singer-songwriter Rina Sawayama covered the song for BBC Radio 1 Live Lounge in 2021 and 2022, respectively.