Professional ratings
Aggregate scores
Source	Rating
Metacritic	72/100
Review scores
Source	Rating
AllMusic
Entertainment Weekly	B+
Los Angeles Times
Melody Maker
NME	5/10
Rolling Stone
The Rolling Stone Album Guide
Slant Magazine
Spin	6/10
The Village Voice	A−

Warning (stylized as WARNING:) is the sixth studio album by American punk rock band Green Day, released on October 3, 2000 by Reprise Records. Building upon its predecessor, Nimrod (1997), the album eschewed the band's trademark punk rock sound and incorporated acoustic elements and pop and folk styles. Lyrically, the record contains more optimistic and inspirational themes in comparison with the band's earlier releases. Warning was also Green Day's first album since Kerplunk (1992) that was not produced by Rob Cavallo, although he did have a hand in its production and was credited as executive producer.

Despite mixed criticism towards the band's stylistic change, the album received mostly positive reviews from music critics, who praised vocalist/guitarist Billie Joe Armstrong's songwriting. Although it peaked at number four on the US Billboard 200 chart, Warning represented the lowest commercial slump in Green Day's career, being the band's first album since signing to a major record label not to achieve multi-platinum status. The album has nonetheless been certified gold by the Recording Industry Association of America and, as of December 2012, has sold 1.2 million copies. Warning was reissued on vinyl on July 14, 2009.

After taking a break from touring in promotion of the band's fourth album Insomniac (1995), Green Day recorded the more experimental Nimrod (1997). The record, which delved into a more wide variety of genres including folk, ska, and surf rock, featured the unprecedented acoustic hit "Good Riddance (Time of Your Life)". Vocalist/guitarist Billie Joe Armstrong recalled that the song's stylistic departure from the group's earlier work made him anxious about the song's release: "I was scared for that song to come out...because it was such a vulnerable song, to put that song out and it was like which way will it end up going? It was really exciting and it kind of sparked more in us as songwriters to expand on that."

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Wikipedia