As a result of the methodology that the American and Canadian certification-awarding bodies (the RIAA and Music Canada respectively) use, each disc in a multi-disc set is counted as one unit toward certification, leading to many double albums on the list—such as Pink Floyd's The Wall and the Beatles' The Beatles—being certified with a number double the number of copies sold there. Such albums have the certifications for the number of copies (not discs) shipped indicated. Conversely, the American certification level for double albums that fit onto one compact disc, such as the Saturday Night Feversoundtrack reflect the actual number of copies sold. In 2016, RIAA included streaming in addition to track sales and album sales based on the concept of album-equivalent unit for certification purposes, and certification therefore no longer reflects shipment alone. For example, in the update of the certification for Their Greatest Hits (1971–1975) by the Eagles in August 2018, the album was certified 38× Platinum (increasing from the previous 29× Platinum certification in 2006) based on the new criteria, making it then the album with the highest certification in the United States.
Michael Jackson's Thriller, estimated to have sold 66 million copies worldwide, is the best-selling album. Although sales estimates for Thriller have been as high as 120 million copies, these sales figures are unreliable. Jackson also currently has the highest number of albums on the list with five, while The Beatles, Madonna and Celine Dion each have three.
Groupings are based on different sales benchmarks, the highest being for claims of at least 40 million copies, and the lowest being for claims of 20–29 million copies. Albums are listed in order of number of copies sold and thereafter by the artist's first name. Markets' order within the table is based on the number of compact discs sold in each market, largest market at the top and smallest at the bottom.