Primarily a downtempo pop record, Happier Than Ever is characterized by sparse, jazz-influenced, electropop arrangements set to meditative tempos, departing from the upbeat, trap-led sound of Eilish's debut album, When We All Fall Asleep, Where Do We Go?

Seven singles were released in promotion of the album: "My Future", "Therefore I Am", "Your Power", "Lost Cause", "NDA", the title track, and "Male Fantasy"; the first three peaked within the top 10 of the US Billboard Hot 100.

[4] In March, Finneas confirmed this, stating that it would be "pretty pure in its intention" like Eilish's debut, with the two continuing to make the type of music they like to "play live".

[8] In an interview with Vevo, Eilish said that she wanted to create "a very timeless record", mostly being inspired by jazz singers that she listened to growing up such as Julie London, Peggy Lee and Frank Sinatra.

[26] It consists of torch songs set to slow tempos, with restrained,[26] minimalistic[22] arrangements of acoustic guitars, delicate synthesizers, and burbling beats.

[29] In Robert Christgau's opinion, Eilish's songwriting had inspired Finneas to devise a sound for the album that is "calmer and less sprightly" than her earlier breakthrough work.

[15] The eleventh track "Everybody Dies", is an alt-pop ballad, driven by dark synths and light guitar strumming, with "Eilish's voice again standing out".

[35] It has been described as "a mopey breakup song", before breaking into "an electric-guitar-driven rager", while the rest of the tracks "bare different kinds of catharsis, teetering between sexy, electronic beats and warm folkiness, reminiscent of her earliest music.

[44] The set was released the following day, featuring vinyls created entirely from leftover recycled materials gathered during the original pressing of the record and a Gucci-branded nail stickers.

[56] For the first anniversary of the album's release, Eilish shared voice memos of her recording takes for "Billie Bossa Nova", "Lost Cause", "Your Power", the title track, and "Male Fantasy".

[57] On June 16, 2021, Eilish performed a 27-minute set on Prime Day Show, including renditions of first four singles from Happier Than Ever, "All the Good Girls Go to Hell", and "Everything I Wanted".

[60] Four renditions of the album's songs were published on the singer's official YouTube account; in chronogical order: "Your Power" on July 18,[61] "Male Fantasy" on August 4,[62] "Lost Cause" on October 21,[63] and "Billie Bossa Nova" on January 13, 2022.

[64] Two additional in-studio performances were uploaded to Eilish's channel, namely "NDA" on July 16, 2021,[65] and an acoustic rendition of "Billie Bossa Nova" on December 20.

[66] On May 8, 2023, a live recording of the song from Billie's set at Lollapalooza Brazil 2023 during the Latin America leg of Happier Than Ever, The World Tour was uploaded to her channel.

[70] On August 5, the singer appeared in BBC Radio 1's Live Lounge with a 4-song set consisting of "Getting Older", "I Didn't Change My Number", "NDA", and a cover of Frances Langford's "I'm in the Mood for Love".

[81][82] Titled Happier Than Ever: A Love Letter to Los Angeles, it was directed by Robert Rodriguez and Patrick Osborne, and it features live action scenes blended with animation.

[83] The concert took place at the Hollywood Bowl without a live audience due to the COVID-19 pandemic;[84] additional scenes were recorded at various landmarks around Los Angeles.

[115] The accompanying music video sparked discourse on social media, that ultimately culminated into an apology posted on the singers Instagram story, as Eilish was accused of queerbaiting.

[118] Despite the song receiving an official studio performance video and radio release in the United States,[119] the single barely scratched Hot 100's top 40, debuted and peaked at number 39, lasting a mere five weeks on the chart.

[131] NME critic El Hunt lauded the album for proving Eilish "one of her generation's most significant pop artists", and wrote that its music is "softer" and "far more low-key" than her debut record.

[28] Alexis Petridis of The Guardian noted the "uniformly great" melodies and vocals, the "less flashy" production in Happier Than Ever, observing a "more somber" tone.

[15] Sal Cinquemani of Slant felt the album is more "sonically diverse" than Eilish's debut record, expanding beyond its predecessor's trip-hop and trap elements.

[32] The Daily Telegraph's Neil McCormick dubbed Happier Than Ever "the sound of a tortured teen alone in her bedroom late at night", its lyrics "pithy", and Eilish's vocals "delicate".

[136] Reviewing in his "Consumer Guide" column, Robert Christgau gave Happier Than Ever an "A" and applauded Eilish for conceiving original ideas about fame through "sheer candor", highlighting her lyrics on "Getting Older", "Not My Responsibility", and "Everybody Dies".

"[21] Rob Sheffield, writing for Rolling Stone, called it a "downright heroic", "dark, painful, confessional album where [Eilish is] choosing not to settle into the role of America's beloved kooky kid sister.

[139] Sarah Carson of i labeled the album a "great, understated, philosophical" project inclining towards sparse and acoustic pop music trends.

[141] Giselle Au-Nhien Nguyen of The Sydney Morning Herald deemed the album a cohesive, "revealing and rewarding, listening experience" enhanced by Eilish's "acidic" delivery.

[143] The New York Times' Lindsay Zoladz felt the album is "fixated on the tension between private and public knowledge, a social-media-era pop star's meditation on how much candor—if any—she owes her audience.

Alexandra Pollard of The Independent remarked that the album is "full of things most of us don't have to deal with", but Eilish turns them into relatable stories via "insightful" songs.

[17] In a mixed review, Matthew Kent of The Line of Best Fit commended Eilish's lyrics and Finneas' production, but regarded the album a less unique work, with its tracks "often blurring into each other.