- The first season had two hosts, Ryan Seacrest and Brian Dunkelman, and three judges, Simon Cowell, Randy Jackson, and Paula Abdul.
- During Hollywood week, contestants sang a song a cappella for the judges. The next day, they formed groups and performed together. In the last round, they sang another song a cappella.
- The semi-final round split the Top 30 into three groups of eight and each group would sing over three consecutive weeks. Viewers voted for three contestants from each group who then advanced to the finals.
- Season 1 also featured a wildcard show where contestants who had not made the cut during their first appearance had another shot at the Top 10. The wildcard picks performed for the judges who then picked one person to advance to the Top 10.
- The live performance shows did not usually have live music and the contestants performed to recorded tracks. During the first performance week, two contestants were eliminated.
- The finale was broadcast live from the Kodak Theatre.
Runner-up: Justin Guarini
3. Nikki McKibbin
4. Tamyra Gray
5. R.J. Helton
6. Christina Christian
7. Ryan Starr
8. A.J. Gil
9/10. EJay Day/Jim Verraros (never determined who had the lowest number of votes)
- Brian Dunkelman was dropped as a host.
- The semi-final rounds were expanded to 32 people and the finals to the Top 12. The Top 32 were split into four groups of eight, with two people from each group advancing to the Top 12.
- In the wildcard round, the judges chose one person to advance and the viewers chose the other.
- The finale was broadcast live from the Gibson Amphitheatre.
Runner-up: Clay Aiken
3. Kimberley Locke
4. Josh Gracin (did not tour due to military obligation)
5. Trenyce
6. Carmen Rasmusen
7. Kimberly Caldwell
8. Rickey Smith
9. Corey Clark (Disqualified)
10. Julia DeMato
11. Charles Grigsby (took Clark’s place on the tour)
12. Vanessa Olivarez
- During the wildcard round, four of the contestants were denied the opportunity to sing for the voters consideration.
- The finale returned to the Kodak Theatre where it remained through Season 7.
Winner: Fantasia Barrino
Runner-up: Diana DeGarmo
3. Jasmine Trias
4. LaToya London
5. George Huff
6. John Stevens
7. Jennifer Hudson
8. Jon Peter Lewis
9. Camile Valasco
10. Amy Adams
11. Matt Rogers
12. Leah LaBelle
- The semi-finals got an extreme makeover. The judges selected a Top 24 – 12 males and 12 females. The group was divided by gender, and each week the girls performed one night and the guys the next. Viewers voted for their favorites, and each week, four were eliminated until only six guys and six girls remained.
- The semi-finals moved from a closed set with no audience to a small theater that had limited seating capacity for family members, friends, and selected guests.
- Rickey Minor’s band became part of all live performance shows.
Runner-up: Bo Bice
3. Vonzell Solomon
4. Anthony Fedorov
5. Scott Savol
6. Constantine Maroulis
7. Anwar Robinson
8. Nadia Turner
9. Nikko Smith
10. Jessica Sierra
11. Mikalah Gordon
12. Lindsey Cardinale
- There were no significant changes made during Season 5.
- Exit song - "Bad Day" by Daniel Powter (a song by a relatively unknown performer that spent five weeks at the top of the Billboard 100)
Winner: Taylor Hicks
Runner-up: Katharine McPhee
3. Elliott Yamin
4. Chris Daughtry
5. Paris Bennett
6. Kellie Pickler
7. Ace Young
8. Bucky Covington
9. Mandisa
10. Lisa Tucker
11. Kevin Covais
12. Melissa McGhee
- The sixth season introduced the American Idol songwriting contest. Songwriters were invited to submit a song for consideration that could ultimately be sung by the Top 2 during the final performance show, becoming the official “coronation” song for the season. The producers selected 20 songs and the public was able to vote for their favorite. “This is My Now,” written by Jeff Peabody and Scott Krippayne won the competition and became the first single released by Jordin Sparks.
- Exit song - "Home" by Daughtry
Winner: Jordin Sparks
Runner-up: Blake Lewis
3. Melinda Doolittle
4. LaKisha Jones
5. Phil Stacey/Chris Richardson
7. Sanjaya Malakar
8. Haley Scarnato
9. Gina Glocksen
10. Chris Sligh
11. Stephanie Edwards
12. Brandon Rogers
- The group round during Hollywood week was eliminated. All the contestants sang on the first day and the judges could issue a pass directly to the last day if they felt the contestant was worthy. Those who were not chosen to automatically advance performed again for their survival.
- Contestants were allowed to play instruments during their performances.
- Exit songs - "Hollywood's Not America" by Ferras, "Best Days" by Graham Colton, and "Celebrate Me Home" by Ruben Studdard
Runner-up: David Archuleta
3. Syesha Mercado
4. Jason Castro
5. Brooke White
6. Carly Smithson
7. Kristy Lee Cook
8. Michael Johns
9. Ramiele Malubay
10. Chikezie
11. Amanda Overmyer
12. David Hernandez
- Executive producer Nigel Lythgoe left the show prior to the start of the eighth season.
- Songwriter Kara DioGuardi was added as a judge.
- The format of the semi-finals changed to include 36 semi-finalists. This group was split into three groups of 12 and the groups performed over the course of three weeks. Viewers voted for their favorites, and each week, three people advanced; the top female, the top male, and the person with the next highest number of votes.
- The wildcard round returned. Each judge chose two contestants for the wildcard performance show. From that group of 12, the judges then chose three contestants to advance to the finals, making it a Top 13 rather than a Top 12.
- Two people were eliminated during the first performance show.
- The judges’ save was introduced allowing the judges to overrule the voters and retain the contestant who received the lowest number of votes should they so desire. The individual would have to perform one more time for the judges before learning his or her fate. The first “save” was used on Matt Giraud in the Top 7.
- Exit song - "Home Sweet Home" by Carrie Underwood
Runner-up: Adam Lambert
3. Danny Gokey
4. Allison Iraheta
5. Matt Giraud
6/7. Lil Rounds/Anoop Desai
8. Scott McIntyre
9. Megan Joy
10. Michael Sarver
11. Alexis Grace
12. Jorge Nunez
13. Jasmine Murray
- Paula Abdul quit the show and was replaced by Ellen DeGeneres
- The semi-final format returned to the that of seasons 4-7 (Guys and girls sing on two separate nights with four eliminated until the Top 12 is revealed)
- Season's exit song - "Leave Right Now" by Will Young
Winner: Lee DeWyze
Runner-up: Crystal Bowersox
3. Casey James
4. Michael Lynche
5. Aaron Kelly
6. Siobhan Magnus
7. Tim Urban
8. Katie Stevens
9. Andrew Garcia
10. Didi Benami
11. Paige Miles
12. Lacey Brown
