The Apple Watch is a line of smartwatches produced by Apple Inc. It incorporates fitness tracking, health-oriented capabilities, and wireless telecommunication, and integrates with iOS and other Apple products and services. The Apple Watch was released in April 2015, and quickly became the best-selling wearable device: 4.2 million were sold in the second quarter of fiscal 2015, and more than 115 million people were estimated to use an Apple Watch as of December 2022. Apple has introduced a new generation of the Apple Watch with improved internal components each September—each labeled by Apple as a 'Series', with certain exceptions.
Each Series has been initially sold in multiple variants defined by the watch casing's material, color, and size (except for the budget watches Series 1 and SE, available only in aluminum, and the Ultra, available only in 49 mm uncolored titanium), and beginning with Series 3, by the option in the aluminum variants for LTE cellular connectivity, which comes standard with the other materials. The band included with the watch can be selected from multiple options from Apple, and watch variants in aluminum co-branded with Nike and in stainless steel co-branded with Hermès are also offered, which include exclusive bands, colors, and digital watch faces carrying those companies' branding.
The Apple Watch operates in conjunction with the user's iPhone for functions such as configuring the watch and syncing data with iPhone apps, but can separately connect to a Wi-Fi network for data-reliant purposes, including communications, app use, and audio streaming. LTE-equipped models can also perform these functions over a mobile network, and can make and receive phone calls independently when the paired iPhone is not nearby or is powered-off, substantially reducing the need for an iPhone after initial setup. The oldest iPhone model that is compatible with any given Apple Watch depends on the version of system software installed on each device.