She said the album explores her perils and discoveries as a 17-year-old, with its title referring to the "sour" emotions young people experience, but are often criticized for, including anger, jealousy, and unhappiness.

Rodrigo's goal for her debut project, Sour, was to create a multifaceted body of work that blends mainstream pop, folk, and alternative rock genres,[12] as well as elements of pop-punk, country, and grunge.

[13] According to Rodrigo, the album was inspired by the works of her favorite singer-songwriters, including Alanis Morissette, Taylor Swift, Kacey Musgraves,[14] and the "pouty", "angsty" sound of rock acts No Doubt and the White Stripes.

So I'm going to try and take all of my sort of influences ... and make something that I like.Rodrigo wrote the album's lyrics to explore a variety of "sour" emotions that young women "are often shamed for", including anger, jealousy, and sadness.

[10] Nevertheless, Rodrigo did not want Sour to be filled with "sad piano songs" either, hence she infused danceability and upbeat arrangements into the record, evident in tracks such as "Brutal" and "Good 4 U".

[26] Rodrigo revealed that she wrote the hook of the song from a text message, going on to say that she "thought it would be a cool way to describe this toxic, sort of manipulative relationship".

[35] The stripped-down tenth track, "Favorite Crime", an indie pop and folk-pop song that incorporates a set of layered harmonies with a "thinly veiled Bonnie and Clyde-type metaphor".

[47] Vinyl LPs of Sour were released on August 20, 2021, in various colored variants, each of which were exclusively available at Rodrigo's webstore, Urban Outfitters, Target, Walmart, or Amazon.

[49][50] Photographed by Grant Spanier,[51] the standard cover artwork of Sour depicts Rodrigo standing against a purple backdrop, wearing a fuzzy pale pink tank top and checkered bottoms.

The backside cover also has a purple background, featuring scattered stickers as well as the tracklist on a pearly-colored balloon that Rodrigo's hand is about to pop with a safety pin.

[55] An accompanying music video for the song, directed by Matthew Dillon Cohen, was uploaded to Rodrigo's YouTube channel simultaneously with the single's release.

"Deja Vu" was announced as the second single on her social media accounts on March 29, 2021, and was released three days later along with its music video, directed by Allie Avital in Malibu.

[65] Its music video, directed by Petra Collins, features Rodrigo as a revengeful cheerleader, making references to the 2000s' cult classic films Princess Diaries and Jennifer's Body.

[66][67] The energetic song provided listeners the taste of a different side of Sour, departing from the slower and melancholic emotion of the preceding singles "Drivers License" and "Deja Vu".

[70][additional citation(s) needed] Before it was promoted as a single, "Traitor" landed at number 9 on the Hot 100 upon the album release, charting alongside "Good 4 U" and "Deja Vu" in the top 10 region.

[78] On May 12, 2021, a trailer to Sour was posted to Rodrigo's YouTube channel, which showed studio clips of herself and Nigro, and featured a snippet of "Good 4 U" which was set to release two days later.

According to a press release, the film captures Rodrigo's road trip from Salt Lake City to Los Angeles, during which she began writing Sour.

He described its 11 tracks as "potential smash hit singles", and complimented Rodrigo's bold lyricism, punchy execution, deeming her "pop's newest icon, and one of its bravest voices".

[103] NME critic Rhian Daly called Rodrigo a "multidimensional" artist writing detailed songs that "go full-circle from being precisely personal to universally relatable".

[27] Neil McCormick of The Daily Telegraph opined Sour excels in modern production, striking an acoustic-electronic balance by combining Taylor Swift's traditional songcraft, Lorde's harmonies, and Billie Eilish's whispery vocals with the brashness of Alanis Morissette and Avril Lavigne.

[19] Also touching on these comparisons, fellow critic Robert Christgau said Rodrigo "recalls her hero Taylor more than her West Coast homegirl Billie with bravely retro pre-track-and-hook structures and lyrics that map out the kind of emotional grounding all parents pray their kids achieve, the female ones especially".

[29] Entertainment Weekly's Maura Johnston felt Sour's heaviness is bettered by Rodrigo's grace and self-awareness, and that she is not trying to be "the next" anyone, but instead distills her life and musical tastes into promising, "powerful, hooky pop".

[26] Rolling Stone critic Angie Martoccio said, beyond her idols and inspirations, Rodrigo forged "a path into an entirely new realm of pop" in Sour, where she is "unapologetically and enthusiastically her own guide".

[106] Variety's Chris Williman called Sour "ridiculously good", and "unabashedly teenage" atypical of most teen singers who often try to mimick adult music.

[109] The Independent critic Helen Brown thought Sour converts 21st-century adolescence into resonating "story-songs", and admired Rodrigo's "disarming honesty", using F-bombs unlike former teen stars who "don't usually do that until they're onto the post-breakdown record".

"[99] Olivia Horn of Pitchfork called it a "nimble and lightly chaotic collection of breakup tunes filled with melancholy and mischief", with profanity typically prohibited by the morality clauses limiting Disney singers.

[31] Rachel Aroesti of The Guardian said Sour is polished "pop euphoria" that processes anger, jealousy and bewilderment, and is "one of the most gratifyingly undignified breakup albums ever made", but nevertheless, majority of it follows the style of "Drivers License", resulting in a lovely and thoughtful but unadventurous record.

[44] Stereogum's Chris DeVille stated, though Rodrigo's lyrics "can come off desperate and immature" while the album's pace can be a "wearisome slog" at times, Sour works by weaponizing its drawbacks.

[110] Regarding the album "a youthful tour through heartbreak angst" that weakens only when it "plays too safe", DIY's Jenessa Williams felt Rodrigo's "truly soars" when she heads strong, rather than victimizing herself in "bitterness".

[111] In a 2024 Billboard cover story, Charli XCX told Kristin Robinson that "she considers 2014's Sucker, for instance, 'an attempt at what Olivia Rodrigo's Sour was able to do much better.