Although auditions can exceed 10,000 in each city, only a few hundred of these made it past the preliminary round of auditions.

Successful contestants then sang in front of producers, where more may be cut.

The eligible age-range for contestants was fifteen to twenty-eight years old. residents, could not have advanced to particular stages of the competition in previous seasons, and must not have held a current recording or talent representation contract by the semi-final stage Contestants went through at least three sets of cuts.

The initial age limit was sixteen to twenty-four in the first three seasons, but the upper limit was raised to twenty-eight in season four, and the lower limit was reduced to fifteen in season ten. The first was a brief audition with a few other contestants in front of selectors which may include one of the show's producers.

, permanent mentors were brought in during the live shows to help guide the contestants with their song choice and performance.

Jimmy Iovine was the mentor in the tenth through twelfth seasons, former judge Randy Jackson was the mentor for the thirteenth season and Scott Borchetta was the mentor for the fourteenth and fifteenth season.

Winners chosen by viewers in its fifteen seasons were Kelly Clarkson, Ruben Studdard, Fantasia Barrino, Carrie Underwood, Taylor Hicks, Jordin Sparks, David Cook, Kris Allen, Lee De Wyze, Scotty Mc Creery, Phillip Phillips, Candice Glover, Caleb Johnson, Nick Fradiani, and Trent Harmon.

American Idol employed a panel of judges who critiqued the contestants' performances.

The original judges were record producer and music manager Randy Jackson, pop singer and choreographer Paula Abdul and music executive and manager Simon Cowell.

The judging panel for the final seasons consisted of country singer Keith Urban, singer and actress Jennifer Lopez, and jazz singer Harry Connick, Jr.

All three original judges stayed on the judging panel for eight seasons.