ITunes



iTunes is a proprietary digital media player application, used for playing and organizing digital music and video files. The application is also an interface to manage the contents on Apple's iPod, iPhone and iPad.

iTunes can connect to the iTunes Store to purchase and download music, music videos, television shows, iPod Games, Audiobooks, Podcasts, movies and movie rentals (not available in all countries), and Ringtones (only available on iPhone and iPod Touch 4th Generation). It is also used to download Apps from the App Store for the iPhone, iPod Touch and iPad.

iTunes was introduced by Apple Inc. on January 9, 2001. The latest version, which is currently version 10.2.2, is available as a free download for Mac OS X v10.5/Windows XP or later on Apple's website. In June 2010, Apple released a new privacy policy pertaining to the capture and collection of users' real-time location information. The information had been included in various device-specific EULAs since 2008, but was only recently included in Apple's general privacy policy.

History
SoundJam MP, developed by Jeff Robbin and Bill Kincaid and released by Casady & Greene in 1999, became the basis for iTunes when Apple purchased it in 2000. Apple added a new user interface and the ability to burn CDs, and removed its recording feature and skin support, and released it as iTunes in January 2001. Originally a Mac OS 9-only application, iTunes began to support Mac OS X when version 2.0 was released nine months later, which also added support for the original iPod. Version 3 dropped Mac OS 9 support but added smart playlists and a ratings system. In April 2003, version 4.0 introduced the iTunes Store; in October, version 4.1 added support for Microsoft Windows 2000 and Windows XP. Version 7.0 introduced gapless playback and Cover Flow in September 2006. In March 2007, iTunes 7.1 added support for Windows Vista, and 7.3.2 was the last Windows 2000 version. iTunes lacked support for 64-bit versions of Windows until the 7.6 update on January 16, 2008. iTunes is currently supported under any 64-bit version of Windows Vista, although the iTunes executable is still 32-bit. The 64-bit versions of Windows XP and Windows Server 2003 are not supported by Apple, but a workaround has been devised for both operating systems. Version 8.0 added Genius playlists, grid view, and a new default visualizer. iTunes 9 added "Home Share" enabling automatic updating of purchased items across other computers on the same subnet and offers a new iTunes Store UI. Genius Mixes were added, as well as improved App synchronization abilities. It also adds iTunes LPs to the store, which gives additional media with an album. Apple added iTunes Extras as well to the store, which adds content usually reserved for films on DVD and Blu-ray discs. Both iTunes LPs and Extras use web-standards HTML, JavaScript and CSS. The latest version of iTunes, iTunes 10, was released by Steve Jobs during a Press Release on September 1, 2010.

A version of iTunes was shipped with cell phones from Motorola, which included the ability to sync music from an iTunes library to the cellphone, as well as a similar interface between both platforms. Since the release of the iPhone, Apple has stopped distributing iTunes with other manufacturers' phones. In the absence of support from Apple, Nokia has released a Mac application called Nokia Multimedia Transfer that supports transferring data from iTunes and iPhoto onto some Nokia devices. Palm however reverse engineered iTunes to allow its Pre device to sync directly with iTunes. It did this by fooling iTunes into thinking the device was an iPod.

In late March 2010, Apple released version 9.1, which has support for the iPad and its iBooks application.

In late June 2010, Apple released version 9.2, which brought support for the new iPhone 4, as well as any iDevices running iOS 4, included support for the new iPhone and iPod Touch version of the iBooks app. It can now install and run on Windows Server 2008 R2.

In September 2010, Apple held their annual music press event where they unveiled an updated version; iTunes 10. The new version was available for download later that day. One major feature include the integration of "iTunes Ping", which brings a social factor to the iTunes experience. Apple CEO; Steve Jobs also announced a new logo, one without a CD in the background because of the increasing popularity of iTunes digital downloads. However, the new logo has begun spanning controversy, as many of iTunes's users favored the usual logo that labeled iTunes as the application it is for almost a decade.

Features
iTunes is an application that allows the user to purchase and manage audio and video on a personal computer, acting as a front end for Apple's QuickTime media player. Officially, using iTunes is required in order to manage the audio of an Apple iPod portable audio player, although alternative software does exist. Users can organize their music into playlists within one or more libraries, edit file information, record Compact Discs, copy files to a digital audio player, purchase music and videos through its built-in music store, download free podcasts, back up songs onto a CD or DVD, run a visualizer to display graphical effects in time to the music, and encode music into a number of different audio formats. There is also a large selection of free internet radio stations to listen to. Additionally, users can add PDF files to their library (to add digital liner notes to their albums, for example), but the PDFs cannot be transferred to or read on an iPod(except for the iPod Touch), but can be read on the iPod Touch, iPhone and iPad. However, iPhone/iPod Touch apps exist to sync any type of file to and from the device to an "iDisk" using Apple's MobileMe service.

In iTunes 8.0, the preferences menu was given a complete makeover. The result added very few new options, but instead removed several options. For example, iTunes once gave users the option to display arrows beside the selected song's title, artist, album, and genre that link directly to the iTunes Store. Now these arrows are not removable, except through the direct editing of a preferences file.

Media management
iTunes keeps track of songs by creating a virtual library, allowing users to access and edit a song's attributes. These attributes, known as metadata, are stored in two separate library files. The first is a binary file called iTunes Library and it uses a proprietary file format ("ITL"). It caches information like artist and genre from the audio format's tag capabilities (the ID3 tag, for example) and stores iTunes-specific information like play count and rating. iTunes typically reads library data only from this file. The second file, iTunes Music Library.xml, is refreshed whenever information in iTunes is changed. It uses an XML format, allowing developers to easily write applications that can access the library information (including play count, last played date, and rating, which are not standard fields in the ID3v2.3 format). Apple's own iDVD, iMovie, and iPhoto applications all access the library. If the first file is corrupted, iTunes will attempt to reconstruct it from the XML file. Detailed third-party instructions regarding this are documented elsewhere. There have been some concerns, voiced by Mark Pilgrim, that this feature will create an "undocumented binary blackhole" because the recovery from the XML file may not work.

It has also been noted that iTunes does not automatically track changes to actual files in the library. If a file is moved or deleted, iTunes will display an exclamation mark beside the library entry and the user will need to manually amend the library record. Several third party tools address this problem.

iTunes supports ripping from CDs, but not from DVDs. However, in 2008, Apple and select film studios introduced "iTunes Digital Copy", a bonus feature on some DVDs that provides a copy-protected, iTunes-compatible file for select films.

File format support
iTunes 10 can currently read, write and convert between MP3, AIFF, WAV, MPEG-4, AAC (.m4a) and Apple Lossless.

iTunes can also play any audio files that QuickTime can play (as well as some video formats), including Protected AAC files from the iTunes Store and Audible.com audio books. There is limited support for Vorbis and FLAC enclosed in an Ogg container (files using the Ogg container format are not naturally supported) or Speex codecs with the Xiph QuickTime Components. Because tag editing and album art is done within iTunes and not QuickTime, these features will not work with these QuickTime components. As of Snow Leopard, iTunes 9 (Mac) will play HE-AAC / AAC+ internet streams. The latest version of iTunes (Win/Mac) supports importing audio CDs with the default iTunes standard file format of AAC at 256 kbit/s, but users can choose from 16 kbit/s to 320 kbit/s constant bit rates (CBR) in either AAC or MP3.

Importing of audio CDs into MP3 or AAC formats can also be accomplished using variable bitrate (VBR) encoding. However, a double-blind experiment conducted in January 2004 of six MP3 encoders noted that the iTunes encoder came last, in that the quality of the files produced by iTunes was below par. It was stated in the final results that these tests only covered VBR encodings, thus iTunes might have performed better with a Constant bitrate (CBR). In a follow-up test performed in October, 2008, iTunes' results were similar to those of the four other MP3 encoders being compared.

The Windows version of iTunes can automatically transcode DRM-free WMA (including version 9) files to other audio formats, but does not support playback of WMA files and will not transcode DRM protected WMA files. Telestream, Inc. provides free codecs for Mac users of QuickTime to enable playback of unprotected Windows Media files. These codecs are recommended by Microsoft.

File metadata
For MP3 files, iTunes writes tags in ID3v2.2 using UCS-2 encoding by default, but converting them to ID3v2.3 (UCS-2 encoding) and ID3v2.4 (which uses UTF-8 encoding) is possible via its "Advanced" > "Convert ID3 Tags" toolbar menu. If both ID3v2.x and ID3v1.x tags are in a file, iTunes ignores the ID3v1.x tags.

Advanced Audio Coding and Apple Lossless files support Unicode metadata, stored in the MPEG-4 Part 14 container as so-called "atoms". The QuickTime plugin that supports the OGG container format has no support for tag editing or album art. iTunes uses the Gracenote interactive audio CD database to provide track name listings for audio CDs. The service can be set to activate when a CD is inserted into the computer and an Internet connection is available. Track names for albums imported to iTunes while not connected to the Internet can be obtained during a later connection, by a manual procedure. For any album loaded into iTunes for which there is not an existing Gracenote track listing, the user can choose to submit track name data to Gracenote.

Information is written down in columns, the information being the number of plays, the date last played, the genre of the music, the album, the composer, the number and the name of the song, but if a song cannot be found on Gracenote iTunes will leave the spaces empty, except the name of the song and the information relating to the plays. These "mystery songs" have been frequently removed from playlists by iTunes users, because they know little about the songs.

Genius
The Genius feature, introduced in iTunes 8, automatically generates a playlist of songs from the user's library which are similar to the selected song. Genius playlists are created by the ratings system and collaborative filtering. An iTunes Store account is required because information about the user's library must first be sent anonymously to Apple's database. Algorithms determine which songs to play based on other users' libraries, and Genius becomes more intelligent given a larger data set. The resulting Genius playlist can contain 25, 50, 75, or 100 songs and can be refreshed for new results or saved. The iTunes Sidebar recommends selections for purchase from the iTunes Store based on the selected library track. Once Genius becomes active in iTunes, it can be used on current generations of the iPod Classic, iPod Nano, iPod Touch or the iPhone. iTunes 9 added Genius Mixes, where the Genius software finds similar music and automatically puts them into mixes.

Library sharing
A user's iTunes Library can be shared over a local network using the closed, proprietary Digital Audio Access Protocol (DAAP), created by Apple for this purpose. DAAP relies on the Bonjour network service discovery framework, Apple's implementation of the Zeroconf open network standard. Apple has not made the DAAP specification available to the general public, only to third-party licensees such as Roku. However, the protocol has been reverse-engineered and is now used to stream audio from non-Apple software (mainly on the Linux platform). DAAP                                                                                                                                                       allows shared lists of songs within the same subnet to be automatically detected. When a song is shared, iTunes can stream the song but won't save it on the local hard drive, in order to prevent unauthorized copying. Songs in Protected AAC format can also be accessed, but authentication is required. A maximum of five users may connect to a single user every 24 hours. The multiple, alternate "View" options normally available to iTunes users including "Cover Flow" are disabled when viewing a shared library over a network.

Library sharing was first introduced with iTunes 4.0, where users could freely access shared music anywhere over the Internet, in addition to one's own subnet, by specifying IP addresses of remote shared song libraries. Apple quickly removed this feature with version 4.0.1, claiming that users were violating the End User License Agreement.

With the release of iTunes 7.0, Apple changed their implementation of DAAP. This change prevents any third-party client, such as a computer running Linux, a modified Xbox, or any computer without iTunes installed, from connecting to a remote iTunes repository. iTunes will still connect as a client to other iTunes servers and to third-party servers.

Library viewing modes
iTunes has four different views for music and video libraries - a song list, an album list, Grid View or Cover Flow.

The standard song list view displays library files with several detail fields.

Album lists are much the same as the standard list view, only the list is broken up by albums, with the artwork as the header of the list. Album lists were introduced in iTunes 10.0, and although this view allows users to browse content more visually, sorting the list view by name will accordingly break up the library into redundant instances of each album.

Cover Flow was introduced in iTunes 7.0 and it displays the album art as CD covers in a sliding format at the top of the screen. Under the album art is a small list of all the songs in that album. Compilation albums are only shown as a single album cover. If there is no album artwork, iTunes will display the default music note pictures.

Grid View is similar to Cover Flow, displaying the user's cover art in a grid rather than a side-scrolling format. While using this view mode, music can be grouped into album, artist, genre, or composer. Grid View was introduced in iTunes 8.0.

iTunes can also sort albums by artist or year, to make its artwork-centered interfaces more intuitive.

Playlists
In addition to static playlist support, version 3 of iTunes introduced support for smart playlists. Smart playlists are playlists that can be set to automatically filter the library based on a customized list of selection criteria, much like a database query. Multiple criteria can be entered to manage the smart playlist.

Any user of iTunes can publish a playlist to the iTunes Store with his or her own preferences, which is called an iMix.

Introduced in iTunes 4.5, the "Party Shuffle" playlist was intended as a simple DJing aid. By default, it selects tracks randomly from other playlists or the library, but users can override the automatic selections by deleting tracks (iTunes will choose new ones to replace them) or by adding their own via drag-and-drop or contextual menu. This allows a mixture of both preselected and random tracks in the same meta-playlist. The playlist from which Party Shuffle drew could be changed on the fly by the computer user, but doing so will cause all randomly chosen tracks to disappear and be replaced.

Party Shuffle was renamed iTunes DJ in iTunes 8. When iTunes was updated to 8.1 quite a few features were added to iTunes DJ. The free Apple Remote application for the iPhone and iPod Touch was also update at this time that added a new iTunes DJ option in the settings screen when the user is connected to a Wi-Fi network and a new song request feature is enabled in iTunes DJ on the hosts. Along with the song request feature voting on songs in the queue was added, the more votes a song gets the high in the queue it will be and sooner it will be played. Song voting can only be done when song requesting is enabled and in two ways: the first by right clicking on a song in the iTunes DJ queue on the hosts computer in iTunes, the second is in the Remote application ether connected with the iTunes DJ option by a guest or by the host in the full playlist section. When song requesting is enabled a customizable welcome message is displayed below the host's shared library name in the button used to connect to iTunes DJ.

Playlists can be played randomly or sequentially. The randomness of the shuffle algorithm can be biased for or against playing multiple tracks from the same album or artists in sequence (a feature introduced in iTunes 5.0, and later discontinued in iTunes 8.0). iTunes DJ can also be biased towards selecting tracks with a higher star rating.

Sound processing
iTunes includes sound processing features, such as equalization, "sound enhancement" and crossfade. There is also a feature called "Sound Check" which automatically adjusts the playback volume of all songs in the library to the same level; this is usually called volume leveling or audio normalization. Like "sound enhancement", this can be turned on in the 'Playback' section of iTunes' preferences.

Video support
On May 9, 2005, video support was introduced to iTunes with the release of iTunes 4.8. Users can drag and drop video clips from the computer into the iTunes Library for cataloguing and organization. They can be viewed in a small frame in the main iTunes display, in a separate window, or fullscreen. Before version 7 provided separate libraries for media types, videos were only distinguished from audio in the Library by a small icon resembling a TV screen and grouped with music in the library, organized by the same musical categories (such as "album" and "composer").

On October 12, 2005, Apple introduced iTunes 6.0, which added support for purchasing and viewing of video content from the iTunes Music Store. The iTunes Music Store initially offered a selection of thousands of Music Videos and five TV shows, including most notably the ABC network's Lost and Desperate Housewives. Disney Channel shows (The Suite Life of Zack & Cody and That's So Raven) were also offered 24 hours after airing, as well as episode packs from past seasons. Since then, the collection has expanded to include content from numerous television networks. The iTunes Music Store also gives the ability to view Apple's large collection of film trailers.

As of September 5, 2006, the iTunes Store offers over 550 television shows for download. Additionally, a catalog of 75 feature-length films from Disney-owned studios was introduced. As of April 11, 2007, over 500 feature-length films are available through iTunes.

Originally, films and TV shows were only available to U.S. customers, with the only video content available to non-U.S. customers being music videos and Pixar's short films. This feature is being extended to other countries as licensing issues are resolved.

Video content available from the store used to be encoded as 540 kbit/s Protected MPEG-4 video (H.264) with an approximately 128 kbit/s AAC audio track. Many videos and video podcasts currently require the latest version of QuickTime, QuickTime 7, which is incompatible with older versions of Mac OS (only v10.3.9 and later are supported). On September 12, 2006, the resolution of video content sold on the iTunes Store was increased from 320x240 (QVGA) to 640x480 (VGA). The higher resolution video content is encoded as 1.5 Mbit/s (minimum) Protected MPEG-4 video (H.264) with a minimum 128 kbit/s AAC audio track.

Books/PDF support
In February 2010, Apple announced the release of the iPad, and along with it they were introducing a new app for it called iBooks. The application performs two functions. The first function is as a direct link to the iTunes book store, called eponymously iBooks, which can only be accessed on iOS devices and not on computers (Mac or PC), by using this app. The second was as a storage place for downloaded books (whether free or purchased) from the iBooks store. The format of books from the Apple store (and the only one users could use with iBooks, until PDF functionality was added later) is ePub.

Additional functions were later added in mid-2010 to include annotations and placeholder/bookmarks in any book being read. Also PDFs were able to be added, and were stored under their own tab in a user's iBooks library, with the same functionality. The iBooks app for the other two iOS devices (iPhone and iPod Touch) was released when iOS 4 was distributed shortly before the release of the iPhone 4.

One current limitation of books (though not PDFs) is that they can only be read using the app on any iOS device and cannot be read inside iTunes on a user's Mac or PC. PDFs can be read using Preview or any other PDF reader/editor application the user has on their machine.

iTunes Store
Version 4 of iTunes introduced the iTunes Store, then named the iTunes Music Store, from which iTunes users can buy and download songs for use on a limited number of computers and an unlimited number of iPods. In previous years, purchased music from the iTunes Store were copy protected with Apple's FairPlay digital rights management (DRM) system which allows protected songs to be played on up to five computers at one time, as well as unlimited devices (iPod, AppleTV, etc.). DRM protected songs can not be played on computers not authorized to the purchaser's iTunes account. At the 2009 Macworld Conference & Expo, it was announced that the iTunes Music Store would be DRM-free, with all songs digital rights management (DRM)-free by April 2009.

Apple also announced changes in their price tier. They announced that songs will now cost $0.69, $0.99, or $1.29, but did not elaborate on how they will be priced. Observers expected new hits to be $1.29 while older songs will be the cheaper $0.99 or $0.69 tier, however many record labels have listed whole catalogs by artists with nothing but $1.29 songs, taking advantage of the price option. Due to this, there are very few songs in the iTunes store with a $0.69 price tag.

In the years since, films, television programs, music videos, podcasts, and the App Store (for the iPhone, iPod Touch and iPad) have been added to iTunes' extensive store catalog.

On January 6, 2009, Phil Schiller announced in his Macworld 2009 keynote speech that over 6 billion songs had been downloaded since the service first launched on April 28, 2003, making it the largest online music store in the world.

At the previous Macworld Expo 2008, Apple CEO Steve Jobs stated that the service had set a new single day record of 20 million songs on December 25, 2007. He also announced that the iTunes Store will offer over 1,000 movies for rental by the end of February. The iTunes movie catalog includes content from 20th Century Fox, Warner Bros., Walt Disney Pictures, Paramount Pictures, Universal Studios, and Sony Pictures Entertainment. These movies will also be transferable to all 6th generation iPods.

On the February 24, 2010, Apple announced that over 10 billion tracks had been downloaded from the iTunes store.

As of Tuesday, November 16, 2010, Beatles fans could download their entire catalog digitally via iTunes. Artists whose music remains largely unavailable include Garth Brooks, AC/DC, Kid Rock, Tool, and Bob Seger. Def Leppard albums are no longer available through iTunes.

iTunes U
On May 30, 2007, Apple announced the launch of "iTunes U" via its digital content Store iTunes which delivers university lectures through a format called iTunesU. The service was created to manage, distribute, and control access to educational audio and video content for students in a college or university, and the whole Internet. Member institutions have the opportunity to have their own iTunes U site, which facilitates searching for material. The online service is free for uploading or downloading these documents. iTunes U includes lectures, language lessons, lab demonstrations, sports, and campus tours provided by many colleges and universities in the United States, United Kingdom, Australia, Canada, Ireland and New Zealand.

Right around the end of 2009/start of 2010, new members institutions no longer have the capability to upload content to Apple's servers. Any member intuitions before that are grandfathered in.

iTunes U has collected materials from a variety of locations around the world, including colleges, universities, museums, libraries and other cultural institutions of educational value. There are currently more than 75,000 files available for download.

In late August 2010, iTunes U surpassed 300 million downloads from 800+ institutions.

Podcasting
Version 4.7 of iTunes, released on June 28, 2005, added built-in support for podcasts.

Users can subscribe to any podcast by entering its RSS feed URL, but also by browsing the podcast directory within iTunes Music Store. The front page of this displays high-profile podcasts from commercial broadcasters and independent podcasters and allows searching by category or popularity. Once subscribed, the podcast can be set to download manually, or automatically — and as with other audio, content can be listened to directly or synced to a portable hardware device like an MP3 player.

The addition of podcasting functionality to such a widespread audio application like iTunes greatly helped podcasting enter the mainstream. Within days after iTunes 4.9 was released, podcasters were reporting that the number of downloads of their audio files had tripled, sometimes even quadrupled, and iTunes is considered the dominant podcast client.

Managing podcasts on an iPod
iTunes offers the ability to create "Smart Playlists" that can be used to control which podcasts are in the playlist, using multiple criteria such as date, number of times listened to, type, etc. It is also possible to set up iTunes so that only certain playlists will be synced with the iPod. By using a combination of the two techniques, it is possible to control exactly which music and/or podcasts will be transferred to the iPod. A user may configure a smart playlist to display only podcasts less than two weeks old or removing any podcast that the iPod user has already listened to. This smart playlist is synced with the iPod every time the iPod is plugged into the PC, ensuring that the user does not have to listen to the same show more than once. Once a podcast has been listened to, it will be removed from this list as soon as the iPod is synced with the PC. There are many criteria which can control what goes in a smart playlist, such as "name," "artist," "category," "grouping," "kind," "last played," "play count," "rating," "last skipped," and "playlist" and these can be combined with functions such as "equals," "is greater than," "is less than," "contains," "is true," "is false," "is," "is not," "does not contain," "starts with," "ends with," "is in the range," "is before," and "is after." As a result, it is possible to control exactly which podcasts are transferred to the iPod.

Video podcasting
Version 6 of iTunes introduced official support for video podcasting, although video and RSS support was already unofficially there in version 4.9.

Users can subscribe to RSS feeds through the iTunes Store or by directly entering the feed URL. Video podcasts can contain downloadable video files (in MOV, MP4, M4V, or MPG format), but also streaming sources and even IPTV.

Downloadable files can be synchronized to a video-capable iPod, or downloadable files and streams can be shown in Front Row.

Synchronizing iPod and other MP3 players
iTunes 2 was the first version of the software to be able to sync with an iPod. iTunes can automatically synchronize its music and video library with an iPod or iPhone every time it is connected. New songs and playlists are automatically copied to the iPod, and songs and playlists that have been deleted from the library on the host computer are also deleted from the iPod. Ratings awarded to songs on the iPod will sync back to the iTunes library and audiobooks will also remember the current playback position.

Automatic synchronization can be turned off in favor of manually copying individual songs or complete playlists. iTunes supports copying music to an iPod; however, only music and videos purchased from the iTunes store can be transferred from the iPod back to iTunes. This functionality was added after third-party software was written which allowed users to copy all content back to their computer. It is also possible to copy from the iPod using ordinary Unix command line tools, or by enabling hidden file viewing in Windows Explorer, then copying music from the iPod drive to a local disk for backup. Doing this can be confusing because the files are arranged in such a way that their folders and (depending on iPod and iTunes versions) file names are seemingly picked at random as they are put on the iPod. It is worth noting, however, that the files (along with their embedded title and artist information) remain unchanged. It is therefore less confusing to let iTunes reimport, reorganize, and rename all of the files after they are backed up. When music or video purchased through the iTunes Store is copied from an iPod, it will only play on computers that are authorized with the account that was used to purchase them. Several third party utilities can remove this limitation by stripping iTunes DRM from protected files. The legality of using such software in the United States is currently the subject of active debate.

When an iPod is connected that does not contain enough free space to sync the entire iTunes music library, a playlist will be created and given a name matching that of the connected iPod. This playlist can then be modified to the user's preference in song selection to fill the available space.

The Mac OS X version of iTunes can also synchronize with a small number of discontinued digital music players, while the Windows version will support only the iPod. The synchronization is limited, however, in that the iPod is the only digital music player compatible with Apple's proprietary FairPlay digital rights management technology, and thus most music purchased through the iTunes Store (before the introduction of iTunes Plus) can only be played on an iPod. The remaining ability to synchronize with a limited number of legacy digital music players is likely a remnant of Apple's timeline the music industry: iTunes was released in January 2001, nine months prior to the iPod's unveiling and slightly more than two years before the introduction of the iTunes Music Store. When iTunes was released, compatibility with other music players was critical; because iPod has become the dominant digital music player, Apple no longer considers that compatibility to be a necessity.

In June 2009, Palm Inc released the Palm Pre which has the ability to sync with both the Windows and Mac OS X version of iTunes by identifying itself to iTunes as an iPod. The Pre is able to sync only DRM-free music. However, on July 14, 2009, Apple released iTunes version 8.2.1 which prevented the Palm Pre from syncing directly with iTunes. Then on July 23, 2009 Palm Inc released WebOS 1.1 which re-enabled syncing between iTunes 8.2.1 and the Palm Pre. But Apple again prevented Palm Pre syncing with the release of iTunes 9.

A number of unsupported third-party applications have been created to help a user of iTunes to synchronize songs with any music player that can be mounted as an external drive. Though iTunes is the only official method for synchronizing with the iPod, there are other applications available that allow the iPod to sync with other software players.

As of iTunes 7, purchased music can be copied from the iPod onto the computer. The computer must be authorized by that iTunes account. iTunes currently allows up to 5 computers to be authorized on one account.To de-authorize and register new computers thereafter, delete all accounts and then register the live one. This can be done only once a year. It does not allow you to transfer imported music files between computers. This may be necessary to back songs up, transfer songs to a new computer, or restore music after a disk failure using an iPod as the backup source. A number of shareware or freeware applications exist that complement iTunes.

iTunes-managed content can also be accessed via the Apple TV set-top box. Files in the iTunes library can either be synchronized with the Apple TV unit, which results in their being copied to the Apple TV's hard drive, or streamed to the Apple TV directly from a Macintosh or PC. Apple TV does not require the use of iTunes (as of the 'Take Two' software update); it can now import files from the iTunes Store directly over the internet.

As of iTunes 9.1, it is possible to sync the iPad to iTunes, allowing music, movies, applications and iBooks to be synced to the iPad.

iPhone activation
Beginning with the introduction of the original iPhone, users can use iTunes to activate their phone through their mobile carrier. The original plan for the iPhone 3G was to have the carrier authenticate it at the point of sale, either through iTunes or through the carrier's own activation interface. However, a worldwide crash of iTunes' authentication servers on July 11, 2008, the day that the iPhone 3G was released, caused major issues. In some cases, AT&T and Apple Store employees told iPhone buyers to attempt to activate it at home. Also affected were original iPhone users attempting to upgrade to the 2.0 firmware. UK Apple, O2 and Carphone Warehouse stores were further impacted, as carrier O2's contract processing servers (known as Gateway) could not handle the amount of new contracts and upgrades happening on launch day. Some stores reverted to hand written contracts, while others held stock. With the launch of the iPhone 3GS on June 19, 2009, iTunes at home activation was available for people purchasing their iPhone from AT&T and Apple. This allowed them to activate their new iPhone 3G/iPhone 3GS at home when they arrived.

Integration with other applications
In Mac OS X, iTunes is tightly integrated with Apple's iWork and iLife suites. These applications can access the iTunes Library directly, allowing access to the playlists and songs stored within (including encrypted music purchased from the iTunes Store). Music files from iTunes can be embedded directly into Pages documents and can supply the score for iDVD, iMovie, and Keynote productions. iTunes is also integrated with Front Row (Front Row compiles its information from the user's iTunes and iPhoto libraries). In addition, any song exported from GarageBand, Apple's basic music-making application, is automatically added to the user's iTunes music library. iTunes's Artwork.saver is a screen saver included in Mac OS X v10.4 that displays album artwork as a screen saver. iTunes widget is a Dashboard Widget that controls iTunes. Moreover, iTunes can be scripted, using AppleScript for Mac OS X or using the Apple-provided SDK for iTunes on Windows allowing many other applications to integrate themselves into iTunes. A common use is to relay the title and artist of what the user is currently listening to into their instant messenger (such as iChat or Microsoft Messenger), or social networking service (such as Facebook or Myspace). LimeWire, which closed on October 26th, 2010, was a peer-to-peer program that provided integration with iTunes, adding songs from LimeWire directly to your iTunes library without sharing your iTunes purchased songs.

Apple Inc. also offers a free iPhone / iPod Touch application called Remote that allows the user to remotely control their iTunes library or Apple TV. This can be downloaded from iTunes itself or directly from one's iPhone / iPod Touch. It is only compatible with iOS v2.0 and above (current version is 4.3). In terms of usage it is very similar (to the extent of almost being identical) to the iPod application that is included with all iPhones, the only difference is the lack of Cover Flow support.

Though iTunes itself can be installed where the user desires, ancillary applications such as Bonjour which are part of the iTunes installation can not be placed in a user-desired directory.

Printing
To compensate for the lack of a physical CD, iTunes can print custom-made jewel case inserts as well as song lists and album lists. After burning a CD from a playlist, one can select that playlist and bring up a dialog box with several print options. The user can choose to print either a single album cover (for purchased iTunes albums) or a compilation cover (for user-created playlists). iTunes then automatically sets up a template with art on one side and track titles on the other.

iMix
An iMix is a user-created playlist published in the iTunes Store. iMixes were first introduced in iTunes version 4.5. Anyone can create an iMix free of charge. iMixes are limited to 100 songs and must feature content available on the iTunes Store. iMixes are public and searchable by any iTunes user. Users may also rate any iMix using a five-star system. iMixes are active for one year from their original published date. Users can publish their iTunes iMix to their blog, profile page or website such as Yahoo! 360°, Facebook, or Myspace.

Internet radio
iTunes came with support for the Kerbango Internet radio tuner service, giving iTunes users a selection of some of the more popular online radio streams available. When Kerbango went out of business in 2001, Apple created its own Internet radio service for use with iTunes 2.0 and later. As of February 2008, the iTunes radio service features 1795 "radio stations," mostly in MP3 streaming format. Programming covers many genres of music and talk, including streams from both internet-only sources and traditional radio stations. iTunes also supports the .pls and .m3u stream file formats used by Winamp and other media players.

Since the release of iTunes 7, Apple no longer promotes the Internet radio feature, though it remains in the application. Some third-parties offer iTunes plugins that add additional radio stations.

In addition, users are able to enter additional stream feeds to listen to in their own music libraries. This is done by selecting the menu item "Advanced" > "Open Audio Stream..." or by the hotkey Ctrl-U (PC) or Command-U (Mac).

Ping
Apple revealed a new feature within iTunes 10 on September 1, 2010 called Ping, which is intended to bring a social music networking factor to users of iTunes. It is not available in all countries yet. Ping can be connected to user's Twitter accounts. Ping connects user accounts of iTunes, allowing iTunes users to share and recommend music to one another.

Plugins
iTunes supports visualizer plugins and device plugins. Visualizer plugins allow developers to create music-driven visual displays. The visualizer plug-in software development kits for Mac and Windows can be downloaded for free from Apple. Device plugins allow support for additional music player devices, but Apple will only license the APIs to authentic OEMs who sign a non-disclosure agreement.

Apple's privacy policy controversy
In June, 2010, Apple updated its general privacy policy for the iTunes Store and iOS4 supported devices, revealing that it could and would collect real-time location-based information on users ages 13 and over. The revised policy states that Apple has the right to share this information with 3rd parties who provide services to the customer, including advertising and promotion services. Apple also states that "it may be necessary" to provide this [real-time] information in response to "requests from public and governmental authorities within or outside your country of residence or if [Apple] determines that for purposes of national security, law enforcement, or other issues of public importance, disclosure is necessary or appropriate"...."Additionally, in the event of a reorganization, merger, or sale we may transfer any and all personal information we collect to the relevant third party." The revised policy does not make any distinction between warrant-based and warrantless searches, nor provide what criteria would trigger the sharing of personal real-time information with government entities, nor allow an opt-out for the location-based information. The revised policy prompted the House Bi-Partisan Privacy Caucus co-chairs to request that Apple respond to nine basic privacy questions out of concern of possible violation of the Federal Communications Act. The Caucus stated it was pleased with Apple's prompt written explanations, and stated they would continue to monitor the issue.

System requirements
Macintosh hardware
 * Mac computer with an Intel, PowerPC G5 or G4 processor
 * Intel, PowerPC G5 or 1.0 GHz PowerPC G4 or faster processor is required to play Standard Definition video from the iTunes Store
 * 2.0 GHz Intel Core 2 Duo or faster processor is required to play HD video, an iTunes LP, or iTunes Extras from the iTunes Store
 * 512MB of RAM; 1GB is required to play HD video, an iTunes LP, or iTunes Extras
 * Screen resolution of 1024x768 or greater; 1280x800 or greater is required to play an iTunes LP or iTunes Extras
 * Playing videos also requires at least 16MB of video RAM
 * Broadband Internet connection to use the iTunes Store
 * Apple combo drive or SuperDrive to create audio, MP3, or back-up CDs; some non-Apple CD-RW recorders may also work.
 * Apple SuperDrive to back up your library to DVDs; some non-Apple DVD-RW drives may also work.

Macintosh software
 * Mac OS X version 10.5 or later
 * QuickTime 7.6 or later
 * Support for HE-AAC requires QuickTime 7.6.4 and Mac OS X version 10.5 or later
 * Safari 4.0.3 or later
 * 200MB of available disk space

Windows hardware
 * A PC with a 1 GHz Intel or AMD processor
 * Intel Pentium D or faster processor is required to play Standard Definition video from the iTunes Store
 * 2.0 GHz Intel Core 2 Duo or faster processor is required to play HD video, an iTunes LP, or iTunes Extras from the iTunes Store
 * 512MB of RAM; 1GB is required to play HD video, an iTunes LP, or iTunes Extras
 * Screen resolution of 1024x768 or greater; 1280x800 or greater is required to play an iTunes LP or iTunes Extras
 * DirectX 9.0-compatible video card with 32MB of video RAM; 64MB recommended
 * QuickTime-compatible audio card
 * Broadband Internet connection to use the iTunes Store
 * iTunes-compatible CD or DVD recorder to create audio CDs, MP3 CDs, or back-up CDs or DVDs

Windows software
 * Windows XP Service Pack 2 or later, 32-bit editions of Windows Vista, or 32-bit editions of Windows 7
 * 64-bit editions of Windows Vista or Windows 7 require the iTunes 64-bit installer
 * QuickTime 7.6.9 or later is required (included)
 * 200MB of available disk space
 * Screen reader support requires Window-Eyes 7.1.1 or later.