Auditionees attempted to do so before a panel of judges, each selected for their background in the music industry  – these have included Cowell, Louis Walsh, Sharon Osbourne, Dannii Minogue, Cheryl, Gary Barlow, Tulisa, Kelly Rowland, Nicole Scherzinger, Mel B, Rita Ora, and Robbie Williams.

[4] The programme itself proved popular on British television,[5] attracting high viewing figures at its peak  – over 14 million on average in the seventh series  – leading to the formation of an international franchise.

In addition, many of its acts, including JLS, Little Mix, One Direction and Ella Henderson, went on to release singles that entered number-one in the UK charts.

[2] The concept for The X Factor stemmed from his involvement as a judge on Pop Idol, another music talent competition that ITV aired from 2001 to 2003.

While the programme had been massively successful in its own right, Cowell disliked the lack of control that he and the judges had on the contestant's progress  – several individuals, including fellow judge Pete Waterman, agreed with him that Michelle McManus who won the second series of Pop Idol had been unworthy to earn victory compared to others who had participated.

In 2004, ITV secured the rights to broadcast The X Factor after Cowell approached them with his concept,[2] despite a legal challenge by Simon Fuller, the creator of Pop Idol, over perceived similarities between the two shows.

Participants are required to provide a performance across each stage, focused on singing a piece from another artist to gauge their musical talent.

[10] Participants that make it to the third stage of auditions then conduct their performance and potential singing talent before the judges for that year's competition.

[11] In the second round, participants who reach this stage are sent to a "bootcamp" to refine their performances, while they are organised into categories based on the conditions of their application.

In some series, some additional participants are sometimes selected from the rejects to act as wildcards in these stages, alongside those who progressed to the live episodes.

The system involves the same phone number, with exception for the last two digits which, beginning at "01", is assigned to each participant by order of appearance.

In March 2007, Thornton was dropped from the programme, with Dermot O'Leary offered a two-year contract, worth £1 million, to take over as host,[22] which eventually led to him ending his involvement in the Big Brother franchise later that year to concentrate on his new role.

However, Friedman dropped out of the panel during auditions for the fourth series, being reassigned as a creative director for the programme, while Walsh agreed to return as a result of this situation.

[29] That same month, Minogue also left the programme, citing that her schedule for the live episodes of Australia's Got Talent that year would conflict with her involvement with The X Factor.

[33][34][35][36][37] During the eighth series, Rowland was unable to attend live episodes for medical reasons, leading to previous X Factor winner Alexandra Burke standing in for her.

[52] In March 2015, O'Leary announced that he was quitting the show in order to pursue other projects, and was replaced a month later by both Olly Murs and Caroline Flack as co-presenters,[53] the latter having served as a backstage presenter since 2013.

[65][66] Cowell was joined on the judging panel by Robbie Williams, Ayda Field and Louis Tomlinson for the fifteenth and final series in 2018.

[67][68] When the programme initially began in 2004, its viewing figures fell behind those for the BBC's rival talent show Strictly Come Dancing.

[74] From 2012 onwards, ratings of The X Factor went into sharp decline  – the tenth series achieved an average viewing audience of 8.5 million viewers, much less than Strictly Come Dancing, with later series proving less popular on Saturday evenings compared to other programmes, such as Michael McIntyre's Big Show and Planet Earth II.

By 2017, ratings for the programme were worse, with The X Factor achieving low average viewing figures of less than seven million viewers, effectively placing its future in doubt after the fifteenth series, and leading to its eventual cancellation.

Recurring allegations include: that the excessive commercialism of the show detracts from its supposed purpose of unearthing musical talent and even actively damages and distorts the UK music industry;[84] that auditionees at mass auditions are shabbily treated; that controversy is deliberately courted and orchestrated, and supposedly spontaneous scenes are staged and scripted; that problems with phone lines leave members of the public unable to vote for their favourite acts; and that contestants are manipulated and unfairly edited.

Nine celebrity acts participated, singing live in front of the nation and facing the judges of the previous The X Factor series: Cowell, Osbourne and Walsh.

The contestants were Michelle Marsh, Nikki Sanderson, Matt Stevens, Lucy Benjamin, Gillian McKeith, Chris Moyles, Paul Daniels and Debbie McGee, James Hewitt and Rebecca Loos, and "The Chefs", a quartet of celebrity chefs comprising Jean-Christophe Novelli, Aldo Zilli, Paul Rankin and Ross Burden.

[101] In November 2019, Cowell announced that The X Factor: The Band would launch on 9 December 2019, with the premise of finding either the biggest male or female group.

[102] The show was won by Real Like You, a girl group composed of Jess Folley, Virginia Hampson, Luena Martinèz, Seorsia Jack, Halle Williams and Kellimarie Willis.

By series 6 in 2009, it had seemingly become such a certainty that the X Factor winner would gain the Christmas number one slot every year that bookmakers William Hill were considering withdrawing from the 30-year tradition of betting on the outcome.

Cowell, Lewis's X Factor mentor and newly appointed manager, said: "We could have gone into the studio for a month, made the record quick, and thrown it out.

He is quoted as saying: "Following last year's record we made with the X Factor finalists in aid of Help for Heroes, we decided we wanted to do something annually on the show to help good causes.

[120] The X Factor brand has also appeared on clothing, jewellery,[124] perfume, make-up, toiletries,[125] bedding, gifts, confectionery,[126] soft drinks[127] and pizzas.

[128] While The X Factor had attracted a large degree of mass appeal from among the British public, become a synonymous part of Saturday night television,[129][130] after its peak in 2010, viewing figures declined by more than 50% over the next decade, with its final series aired in 2018.