At the age of 17, Blige recorded a cover version of Anita Baker's "Caught Up in the Rapture" in a recording booth at a local mall. Her mother's boyfriend at the time later played the cassette to recording artist and A&R runner for Uptown Records, Jeff Redd. Redd then sent it to the president and chief executive officer of the label, Andre Harrell. Blige met with Harrell in 1990 and performed the song for him. She was signed to Uptown and became the label's youngest and third female recording artist (after Finesse N' Synquis).
After being signed to Uptown Records, Blige began working with record producer Puff Daddy. He became the executive producer and produced a majority of the album. The title, What's the 411?, derived from Blige's past occupation as a 4-1-1 operator; it was also an indication by Blige of being the "real deal". The music was described as "revelatory on a frequent basis". Blige was noted for having a "tough girl persona and streetwise lyrics". The album begins with "Leave a Message", a collection of Blige's answering machine messages over a drum beat. The following two tracks, "Reminisce" and "You Remind Me", are melancholy songs that are overlaid with hip hop beats. A cover of Chaka Khan's "Sweet Thing" followed.
What's the 411? was released on July 28, 1992, to positive reviews from critics. In Entertainment Weekly, Havelock Nelson hailed it as "one of the most accomplished fusions of soul values and hip-hop to date" while comparing Blige's "powerful voice" to Khan, Anita Baker, and Caron Wheeler. Connie Johnson from the Los Angeles Times was particularly impressed by her rendition of "Sweet Thing" and "You Remind Me", calling the latter track "one of those perfect singer-to-song matches".People magazine said the album succeeded because of Blige's "fly-girl attitude" and singing ability, even though "she may not be Chaka Khan or Gladys Knight". Mitchell May was more critical in the Chicago Tribune, writing that aside from the title track and "Sweet Thing", What's the 411? was marred by dull production and "silly lyrics" depriving the singer of self-esteem.Village Voice critic Robert Christgau was largely unimpressed, grading the album a "dud" in his consumer guide. He later upgraded his score to a one-star honorable mention—indicating "a worthy effort that consumers attuned to its overriding aesthetic or individual vision may well like"; he named "Sweet Thing" and "Real Love" as highlights while writing that "real is not enough, but attached to the right voice it's something to build on".
What's the 411? peaked at number six on the Billboard 200 and topped the Top R&B/Hip-Hop Albums chart. It also peaked at number 53 on the UK Albums Chart. It was certified three times Platinum by the RIAA. According to Entertainment Weekly's Dave DiMartino, with the record's commercial success and Blige's "powerful, soulful voice and hip-hop attitude", she "solidly connected with an audience that has never seen a woman do new jack swing but loves it just the same". According to Dave McAleer, Blige became the most successful new female R&B artist of 1992 in the United States.What's the 411? earned her two Soul Train Music Awards in 1993: Best New R&B Artist and Best R&B Album, Female. It was also voted the year's 30th best album in the Pazz & Jop—an annual poll of American critics nationwide, published by The Village Voice. By August 2010, the album had sold 3,318,000 copies in the US.
What's the 411? has since been viewed by critics as one of the 1990s' most important records. Blige's combination of vocals over a hip hop beat proved influential in contemporary R&B. With the album, she was dubbed the reigning "Queen of Hip Hop Soul", Stanton Swihart wrote in a retrospective review for AllMusic. He called it "the decade's most explosive, coming-out displays of pure singing prowess". According to David O'Donnell from BBC Music, What's the 411? was groundbreaking in its fusion of R&B hooks and hip hop beats, creating the formula for the contemporary R&B of the following decade. He complimented Blige's "sweet, soulful vocals", in line with Puff Daddy's "rough, jagged, hip-hop beats made for a winning combination that remains one of Blige's finest albums". In The Rolling Stone Album Guide (2004), Tom Moon wrote that with the album, Blige offered "a gritty undertone and a realism missing from much of the devotional love songs ruling the charts at that time."