A mobile operating system designed and created by Apple Inc. specifically for its hardware is known as iOS (previously iPhone OS). Since version 13, it has served as the operating system for many of Apple's mobile devices, including the iPhone and iPod Touch; however, before the moniker iPadOS was established with version 13, it was used to refer to the versions running on iPads as well. It is the world's second-most commonly used mobile operating system, behind only Android in terms of total installed bases. iPadOS, tvOS, and watchOS are all operating systems developed by Apple that are based on the iOS platform. Even though certain components of it are open source under the Apple Public Source License and other licences, it is proprietary software.
iOS, which was originally launched in 2007 for the first-generation iPhone, has subsequently been expanded to include additional Apple devices such as the iPod Touch (which was introduced in September 2007) and the iPad (which was introduced in March 2010). (introduced: January 2010; availability: April 2010.) The Apple App Store has more than 2.1 million iOS apps as of March 2018, with 1 million of them being designed specifically for iPad. More than 130 billion copies of these mobile applications have been downloaded worldwide.
On an annual basis, Apple releases major updates to its iOS operating system. iOS 15 was released to the general public on September 20, 2021, and is the most recent stable version of the software.