The final result was primarily a dance-pop and electropop record with Euro disco and dubstep influences, with lyrical themes revolving around love, fame, media scrutiny, sex, and clubbing.

Initial reviews were polarized: some critics described it as Spears' most progressive and consistent album to date, while others dismissed it due to her controversial public image.

"Gimme More" peaked at number three on the US Billboard Hot 100, becoming her highest-peaking single on the chart since "...Baby One More Time" (1998), and reached the top ten in additional 16 countries.

In retrospect, the album has been deemed a career highlight for Spears and has been praised for its significant impact on the ensuing 2010s decade of pop music, being credited for bringing the electropop and avant-disco genres to mainstream prominence.

"[3] However, on December 30, she made a surprise appearance at the Los Angeles radio station KIIS-FM to premiere a rough mix of a new midtempo track "Mona Lisa".

She also revealed she wanted the song to be the lead single from her upcoming album, tentatively titled The Original Doll, and hoped to release it "probably before summertime [2005], or maybe a little sooner than that.

[8] In an interview with People in February 2006, Spears explained that she was anxious to resume her career, commenting she missed "traveling [...] the road, seeing different places and being with the dancers and having fun.

[27] On November 8, the day after she filed for divorce from Federline, Spears recorded "Radar" with Ezekiel Lewis and Patrick M. Smith of the Clutch at the Sony Music Studios in New York City.

Both commented that although Spears arrived late to the recording sessions, she caught them off guard with her efficiency and professionalism, with Lewis adding: "It was absolutely nuts, and she took directions very well.

Danja stated that Spears' objective was to make Blackout a fun, danceable album with uptempo, high-energy music, saying: "She wanted to stay away from being personal.

[45] The next track and second single "Piece of Me" runs through a down-tempo dance beat and consists of over-the-top vocal distortions, causing a split sound effect and making it difficult to discern which voice is Spears'.

[46][47] The third track "Radar" is an electropop and Eurodisco song which features distorted synthesizers emulating sonar pulses, that received comparisons to those of Soft Cell's "Tainted Love" (1981).

Jeff Leeds of The New York Times said that "no one was prepared for Sunday night's fiasco, in which a listless Ms. Spears teetered through her dance steps and mouthed only occasional words in a wan attempt to lip-synch her new single".

[69] The following day, Zomba Label Group filed a lawsuit against Perez Hilton, claiming he illegally obtained and posted on his gossip blog at least ten songs and unfinished demos of the album.

[74] It also peaked atop the Canadian Hot 100 and within the top five in Australia, Belgium, Croatia, Denmark, France, Ireland, Italy, Norway, Sweden, Switzerland, Ukraine and the United Kingdom.

[81] It peaked at number one in Ireland and within the top ten in Australia, Austria, Canada, the Commonwealth of Independent States, Denmark, Finland, France, Germany, New Zealand, Slovakia, Sweden and the United Kingdom.

[83] Its accompanying music video, directed by Wayne Isham, portrayed Spears' life at the time and showed her with her friends disguising themselves in order to confuse the paparazzi.

[93] Stephen Thomas Erlewine, senior editor of AllMusic, described the album as "state-of-the-art dance-pop, a testament to skills of the producers and perhaps even Britney being somehow cognizant enough to realize she should hire the best, even if she's not at her best.

"[96] Pitchfork's Tom Ewing called "Get Naked (I Got a Plan)" the centerpiece of Blackout, and branded the album "superb modern pop, which could probably only have been released by this star at this moment.

"[63] Melissa Maerz from Rolling Stone explained that the album "is the first time in her career that she's voiced any real thoughts about her life" and that "she's gonna crank the best pop booty jams until a social worker cuts off her supply of hits.

"[50] Kelefa Sanneh of The New York Times said: "The electronic beats and bass lines are as thick as Ms. Spears's voice is thin, and as the album title suggests, the general mood is bracingly unapologetic."

Sanneh added that Spears had a spectral presence on the album, explaining that when compared to her previous records, "[she] cuts a startlingly low profile on Blackout [...] Even when she was being marketed as a clean-cut ex-Mouseketeer, and even when she was touring the country with a microphone that functioned largely as a prop, something about her was intense.

"[42] Peter Robinson of The Observer stated that Spears "delivered the best album of her career, raising the bar for modern pop music with an incendiary mix of Timbaland's Shock Value and her own back catalogue.

Kheraj also said that the album "was the result of a hazardous moment in pop culture history that saw a serendipitous and symbiotic relationship between an artist eroding her past and producers forging their future that payed [sic] off.

At night, it was announced through an article on Billboard.biz that after an agreement with Nielsen SoundScan, Billboard would allow exclusive albums only available through one retailer to appear on the charts, effective that same week.

[129] As of March 2015, the album has sold one million copies in the country, and was certified double platinum by the Recording Industry Association of America (RIAA) in October 2023.

[147] Tom Ewing of Pitchfork noted that after "Freakshow" leaked online, a dubstep forum thread on the song hit seven pages in twenty-four hours, generating mixed reactions and exemplifying that "it still seems [that] when the mainstream borrows underground music, [it] brings it into the wider pop vocabulary."

[47][148] Ewing said that Blackout serves as a reminder of how instantly recognizable Spears' vocals are, saying that "treated or untreated: her thin Southern huskiness is one of the defining sounds of 00s pop."

"[47] While reviewing Spears' demo of "Telephone", Rob Sheffield of Rolling Stone compared it to "Piece of Me", "proving yet again how much impact Britney has had on the sonics of current pop.

"[150] The Independent ranked Blackout number three on their list of the 20 most underrated albums ever, with Roisin O'Connor crediting the "icy beats and glitchy synths" of "Piece of Me" for inspiring "generations of future-leaning pop stars in the decades to come.