The iPhone's hardware is designed by Apple Inc. Apple directly sub-contracts hardware production to external OEM companies, maintaining a high degree of control over the end product.
Screen and input
The touchscreen on the iPhone has increased in size several times over the years, from 3.5 inches on the original iPhone to iPhone 4S, to the current 6.1 and 6.7 inches on the iPhone 14 and 14 Pro series. The touch and gesture features of the iPhone are based on technology originally developed by FingerWorks. Most gloves and styli prevent the necessary electrical conductivity; although capacitive styli can be used with iPhone's finger-touch screen. The iPhone 3GS and later also feature a fingerprint-resistant oleophobic coating.
The iPhone has a minimal hardware user interface, with most models featuring five buttons. The only physical menu button is situated directly below the display and is called the "Home button" because its primary function is to close the active app and navigates to the home screen of the interface. Earlier models included a rounded square, reminiscent of the shape of icons on the home screen. However, new models which include Apple's fingerprint recognition feature Touch ID (which use the Home button as the fingerprint sensor) have no symbol. The iPhone X and later, with the exception of the iPhone SE series, do not have a Home button, and include Face ID in place of Touch ID, a facial recognition authentication method.
A multi-function sleep/wake button is located on top of the device on earlier models, and on right of the device from iPhone 6 onwards. It serves as the unit's power button, and also controls phone calls. When a call is received, pressing the sleep/wake button once silences the ringtone, and when pressed twice transfers the call to voicemail. Situated on the left spine are the volume adjustment controls. The iPhone 4 has two separate circular buttons to increase and decrease the volume; all earlier models house two switches under a single plastic panel, known as a rocker switch, which could reasonably be counted as either one or two buttons.
Directly above the volume controls is a ring/silent switch that, when engaged, mutes phone calls ringtones, alert sounds from push notifications, and system sound effects.
3D Touch and Haptic Touch
The iPhone 6S and 6S Plus, introduced in 2015, feature 3D Touch displays which allow the screen to recognize how hard it is being pressed using pressure-sensitive multi-touch technology, and a new Taptic Engine to provide haptic feedback. In addition to visual cues, 3D Touch uses the Taptic Engine to provide a tactile sensation relative to the force being applied to the display to indicate to the user that a light or deep press action has been completed. An example of how this technology was used is lightly pressing the screen to preview a photograph and deeply pressing to open it, a feature dubbed 'Peek and Pop' by Apple.
All iPhones starting with the iPhone 6s (with the exception of the first-generation iPhone SE and iPhone XR) had this feature. Starting in 2019 however, 3D Touch was omitted on all iPhones starting with the iPhone 11 and 11 Pro series, and its software features were removed from iOS 13 and later in favour of Haptic Touch. Haptic Touch retains much of the functionality of 3D Touch but cannot detect pressure, as the display lacks integrated capacitive sensors. Actions that previously required a deep press now only require a long press, and the haptic feedback is no longer associated with the applied pressure but rather the touch duration. iPad models that can update to iPadOS 13, along with the first-generation iPhone SE and seventh-generation iPod touch, which previously did not support 3D Touch, simultaneously gained similar Haptic Touch functionality with the iOS 13 and iPadOS 13 updates, although without any haptic feedback.
Sensors
iPhones feature a number of sensors, which are used to adjust the screen based on operating conditions, enable motion-controlled games, location-based services, unlock the phone, and authenticate purchases with Apple Pay, among many other things.
Proximity sensor
A proximity sensor deactivates the display and touchscreen when the device is brought near the face during a call. This is done to save battery power and to prevent inadvertent inputs from the user's face and ears. The iPhone's proximity sensors detect the ear and switches off the light, saving power and stopping the face from unintentionally pressing buttons. A phone case, dirt or grime, or a software problem may cause the proximity sensor to malfunction.