Three months after the track's release, Hayley Williams and Josh Farro were retrospectively given co-writing credits due to influence from Paramore's "Misery Business" (2007),[2] with the pair to receive a combined royalty share of 50%.

It consists of a staccato bassline, energetic electric guitars, and explosive drumming, with lyrics addressing a former lover who moved on very quickly after a breakup.

The accompanying music video features Rodrigo as a high-school cheerleader exacting revenge, visually alluding to the 2000s films Audition, The Princess Diaries, and Jennifer's Body.

[4] On May 10, Rodrigo announced via her social media accounts that "Good 4 U" would become the third single from Sour on May 14, following "Drivers License" and "Deja Vu".

[20][21][22] However, it was later reported by Variety that Rodrigo's camp had been in contact with Williams and Farro prior to the song's release and they were eventually paid between $700k–$1.2m in royalties.

[23][24] Rodrigo publicly responded, discussing her feelings about Williams and Farro being added as co-writers on "Good 4 U": "I think it's disappointing to see people take things out of context and discredit any young woman's work.

The second verse returns to the original bass line with added "lilting" drum beats and backup harmonies and slowly ascends to Rodrigo's "near-shout" vocal delivery.

It marks a departure from Rodrigo's preceding singles, "Drivers License" and "Deja Vu", which presented a melancholic and slower emotion.

"[27] Rob Sheffield of Rolling Stone lauded Rodrigo's musical versatility, and noted influences from Taylor Swift in "Good 4 U".

[13] Variety critic Ellise Shaffer dubbed the song a "nostalgic heartbreak anthem" evoking a "fluttering, cathartic feeling reminiscent of late '90s Hole or early Paramore, but with a poppier flair".

Dodson found Rodrigo's voice versatile, easily moving between styles similar to Swift's vocals in "We Are Never Ever Getting Back Together" (2012), and that of Alanis Morissette and Hayley Williams, to become "something original".

[28] Sydney Bucksbaum, writing for Entertainment Weekly, called the single a "pop-punk breakup anthem" and an "immediate banger", underlining the song's similarities to Paramore's "Misery Business" (2007).

"[10] In the United States, "Good 4 U" debuted atop the Billboard Hot 100, giving Rodrigo her second number-one song in the country, following her eight-week chart-topper "Drivers License".

[52] "Good 4 U" became one of the biggest chart-topping singles in the UK in 2021, gathering more than 117,000 units sold in its second week, including 13.5 million streams, to reach number one.

[61] In Ireland "Good 4 U" scored Rodrigo's second number-one song on the Official Irish Singles Chart, following "Drivers License".

stated that "Good 4 U" leads the commercial comeback of rock music in 2020–2021, noting how it is the first rock record since Evanescence's 2003 single "Bring Me to Life" to spend four or more weeks atop the UK Singles chart, alongside chart success of other rock-adjacent artists, such as Willow Smith, Machine Gun Kelly, Måneskin, and Miley Cyrus.

[14] Slate admired Rodrigo's versatility and proclaimed that she "might be the dying genre's best hope", pinpointing that "Good 4 U" is the "most up-the-middle rock song to top the [U.S.] Hot 100 in a decade or more".

In the video, Rodrigo appears in a variety of looks, including a cheerleading uniform seen in the 2001 coming-of-age film The Princess Diaries (also seen in the cover artwork).

[26] Insider critic Callie Ahlgrim opined that the fire was a reference to Swift's music video for "Picture to Burn" (2008), which also follows a similar revenge concept.