An app store (or app marketplace) is a type of digital distribution platform for computer software, often in a mobile context. Apps provide a specific set of functions which, by definition, do not include the running of the computer itself. Apps are designed to run on specific devices, and are written for a specific operating system (such as iOS, macOS, Windows, or Android). Complex software designed for use on a personal computer, for example, may have a related app designed for use on a mobile device.
Such a mobile app may offer similar, if limited, functionality compared to the complete software running on the computer. Apps optimize the appearance of displayed data, taking into consideration the device screen size and resolution. Besides providing continuity of functionality over two different types of devices, such apps may also be capable of a file synchronization between two dissimilar devices, even between two different operating system platforms. App stores typically organize the apps they offer based on these considerations: the function(s) provided by the app (including games, multimedia or productivity), the device for which the app was designed, and the operating system on which the app will run.
App stores typically take the form of an online store, where users can browse through these different app categories, view information about each app (such as reviews or ratings), and acquire the app (including app purchase, if necessary - many apps are offered at no cost). The selected app is offered as an automatic download, after which the app installs. Some app stores may also include a system to automatically remove an installed program from devices under certain conditions, with the goal of protecting the user against malicious software.
Many app stores are curated by their owners, requiring that submissions of prospective apps go through an approval process. These apps are inspected for compliance with certain guidelines (such as those for quality control and censorship), including the requirement that a commission be collected on each sale of a paid app. With the ease of use apps offer, and their presence on most mobile devices, app stores rose to prominence at the beginning of the 21st century with their adoption by iOS (iOS App Store) and Android (Google Play). Similar systems for the distribution of apps written for other operating systems have also been available for some time (particularly Linux distributions since the early 1990s), through package management systems and their graphical front-ends.
The Electronic AppWrapper  was the first commercial electronic software distribution catalog to collectively manage encryption and provide digital rights for apps and digital media (issue #3 was the app store originally demonstrated to Steve Jobs at NeXTWorld EXPO). While a Senior Editor at NeXTWORLD Magazine, Simson Garfinkel, rated The Electronic AppWrapper 4 3/4 Cubes (out of 5), in his formal review. Paget's Electronic AppWrapper was named a finalist in the highly competitive InVision Multimedia '93 awards in January, 1993 and won the Best of Breed award for Content and Information at NeXTWORLD Expo in May, 1993.
Many Linux distributions and other Unix-like systems provide a tool known as a package manager, which allows a user to automatically manage the software installed on their systems (including both operating system components and third-party software) using command line tools—new software (and the packages required for its proper operation) can be retrieved from local or remote mirrors and automatically installed in a single process. Notable package managers in Unix-like operating systems have included pkgsrc (1997), Debian's APT (1998), YUM, and Gentoo's Portage (which unlike most package managers, distributes packages containing source code that is automatically compiled instead of executables). Some package managers have graphical front-end software which can be used to browse available packages and perform operations, such as Synaptic (which is often used as a front-end for APT).
In 1996, the SUSE Linux distribution has YaST as frontend for its own app repository. Mandriva Linux has urpmi with GUI frontend called Rpmdrake. Fedora and Red Hat Enterprise Linux has YUM in 2003 as a successor of YUP (developed at Duke University for Red Hat Linux).
In 1997, BeDepot a third-party app store and package manager (Software Valet) for BeOS was launched, which operated until 2001. It was eventually acquired by Be Inc. BeDepot allowed for both commercial and free apps as well as handling updates
In 1998, Information Technologies India Ltd (ITIL) launched Palmix, a web based app store exclusively for mobile and handheld devices. Palmix sold apps for the three major PDA platforms of the time: the Palm OS based Palm Pilots, Windows CE based devices, and Psion Epoc handhelds.
In 1999, NTT DoCoMo launched i-mode, the first integrated online app store for mobile phones, gaining nationwide popularity in Japanese mobile phone culture. DoCoMo used a revenue-sharing business model, allowing content creators and app providers to keep up to 91% of revenue.
In December 2001, Sprint PCS launched the Ringers & More Wireless Download Service for their then-new 3G wireless network. This allowed subscribers to the Sprint PCS mobile phone network to download ringtones, wallpaper, J2ME applications and later full music tracks to certain phones. The user interface worked through a web browser on the desktop computer, and a version was available through the handset.
In 2002, the commercial Linux distribution Linspire (then known as LindowsOS—which was founded by Michael Robertson, founder of MP3.com) introduced an app store known as Click'N'Run (CNR). For an annual subscription fee, users could perform one-click installation of free and paid apps through the CNR software. Doc Searls believed that the ease-of-use of CNR could help make desktop Linux a feasible reality.
In 2003 Handango introduced the first on-device app store for finding, installing and buying software for smartphones. App download and purchasing are completed directly on the device so sync with a computer is not necessary. Description, rating and screenshot are available for any app.
The popular Linux distribution Ubuntu (also based on Debian) introduced its own graphical software manager known as the Ubuntu Software Center on version 9.10 as a replacement for Synaptic. On Ubuntu 10.10, released in October 2010, the Software Center expanded beyond only offering existing software from its repositories by adding the ability to purchase certain apps (which, at launch, was limited to Fluendo's licensed DVD codecs).
In 2007, Apple Computer launched the iPhone, the company's first ever smartphone. When the device launched, the device did not provide any support for third-party software: Apple's CEO Steve Jobs believed that web apps served over the internet could provide adequate functionality required for most users. Soon after its release, however, developers had managed to "jailbreak" the iPhone and begin coding third-party apps for the device, distributed through package managers such as Installer.app (which itself was based on APT) and Cydia.
With the release of iPhone OS 2.0 in July 2008, Apple launched the App Store, officially introducing third-party app development and distribution to the platform. The service allows users to purchase and download new apps for their device through either the App Store on the device, or through the iTunes Store on the iTunes desktop software. Apple asserts a large number of restrictions on app developers: all apps are subject to a review by Apple staff when submitted and can be rejected if they do not pass Apple's technological and content guidelines. Additionally, Apple takes a 30% commission on revenues for paid apps sold through the store. Even after the launch of the official App Store, alternative app stores for jailbroken iOS devices, such as Cydia (which also introduced the ability to charge for apps), have remained active as an alternative platform to allow developers to distribute apps that have been rejected by Apple, or for those who do not wish to distribute through the App Store.
While Apple has been criticized by some for how it operates the App Store, it has been a major financial success for the company: reaching over 40 billion app downloads as of 2013[update], with a library of over 800,000 apps available. The popularity of Apple's App Store led to the introduction of equivalent marketplaces by competing mobile operating systems: the Android Market (later renamed to Google Play) launched alongside the release of the first Android smartphone (the HTC Dream) in September 2008, and BlackBerry's App World launched in April 2009. In January 2011, Apple also launched the Mac App Store, a similar distribution platform for macOS software on Macintosh computers; while developers can still distribute apps for Macs via traditional methods, the Mac App Store features similar certification requirements to its iOS counterpart to ensure security and reliability.
In 2016, Apple announced that several outdated and low quality apps will be removed from the App Store to improve the quality of the platform.
Due to its popularity, the term "app store" (first used by the Electronic AppWrapper  and later popularized by Apple's App Store for iOS devices) has frequently been used as a generic trademark to refer to other distribution platforms of a similar nature. Apple asserted trademark claims over the phrase, and filed a trademark registration for "App Store" in 2008. In 2011, Apple sued both Amazon.com (which runs the Amazon Appstore for Android-based devices) and GetJar (who has offered its services since 2004) for trademark infringement and false advertising regarding the use of the term "app store" to refer to their services. Microsoft filed multiple objections against Apple's attempt to register the name as a trademark, considering it to already be a generic term.
In January 2013, Apple's claims were rejected by a US District judge, who argued that the company presented no evidence that Amazon had "[attempted] to mimic Apple’s site or advertising", or communicated that its service "possesses the characteristics and qualities that the public has come to expect from the Apple APP STORE and/or Apple products" In July 2013, Apple dropped its case.