With the 2003 addition of the iTunes Store for purchasing and downloading digital music, and a Windows version of the program, it became an ubiquitous tool for managing music and configuring other features on Apple's line of iPod media players, which extended to the iPhone and iPad upon their introduction.

The primary developers of the software moved to Apple as part of the acquisition, and simplified SoundJam's user interface, added the ability to burn CDs, and removed its recording feature and skin support.

Each track has attributes, called metadata, that can be edited by the user, including changing the name of the artist, album, and genre, year of release, artwork, among other additional settings.

[22] File metadata is displayed in users' libraries in columns, including album, artist, genre, composer, and more.

[24] Introduced in 2004,[25] "Party Shuffle" selected tracks to play randomly from the library, though users could press a button to skip a song and go to the next in the list.

[29] "Genius" transmits information about the user's library to Apple anonymously, and evolves over time to enhance its recommendation system.

[30] The feature was updated with iTunes 9 in 2009 to offer "Genius Mixes", which generated playlists based on specific music genres.

[35] Computer firewalls must allow network traffic, and users must specifically enable sharing in the iTunes preferences menu.

[38][39] Introduced on April 28, 2003, The iTunes Music Store allows users to buy and download songs, with 200,000 tracks available at launch.

[40] Music purchased was protected by FairPlay, an encryption layer referred to as digital rights management (DRM).

[41] The use of DRM, which limited devices capable of playing purchased files,[42] sparked efforts to remove the protection mechanism.

[56] At launch, the store offered popular shows from the ABC network, including Desperate Housewives and Lost, along with Disney Channel series That's So Raven and The Suite Life of Zack & Cody.

CEO Steve Jobs told the press that "We're doing for video what we've done for music — we're making it easy and affordable to purchase and download, play on your computer, and take with you on your iPod.

[64] In September 2017, Apple updated iTunes to version 12.7, removing the App Store section in the process.

[76] The Telegraph reported in November 2011 that Apple had been aware of a security vulnerability since 2008 that would let unauthorized third parties install "updates" to users' iTunes software.

"[77] iTunes has been repeatedly accused of being bloated as part of Apple's efforts to turn it from a music player to an all-encompassing multimedia platform.

[65][78][79][80][81] Former PC World editor Ed Bott accused the company of hypocrisy in its advertising attacks on Windows for similar practices.