The battery life of early models of the iPhone has been criticized by several technology journalists as insufficient and less than Apple's claims. This is also reflected by a J. D. Power and Associates customer satisfaction survey, which gave the "battery aspects" of the iPhone 3G its lowest rating of 2 out of 5 stars.

If the battery malfunctions or dies prematurely, the phone can be returned to Apple and replaced for free while still under warranty. The warranty lasts one year from purchase and can be extended to two years with AppleCare. Though the battery replacement service and its pricing was not made known to buyers until the day the product was launched, it is similar to how Apple (and third parties) replace batteries for iPods. The Foundation for Taxpayer and Consumer Rights, a consumer advocate group, has sent a complaint to Apple and AT&T over the fee that consumers have to pay to have the battery replaced. Since July 2007, third-party battery replacement kits have been available at a much lower price than Apple's own battery replacement program. These kits often include a small screwdriver and an instruction leaflet, but as with many newer iPod models the battery in the original iPhone has been soldered in. Therefore a soldering iron is required to install the new battery. The iPhone 3G uses a different battery fitted with a connector that is easier to replace. 

The original iPhone and iPhone 3G feature a built-in Fixed focus 2.0 megapixel camera located on the back for still digital photos. It has no optical zoom, flash or autofocus, and does not support video recording (iPhone 3G does support video recording via third-party App available on the App Store), howeverjailbreaking allows users to do so. Version 2.0 of iPhone OS introduced the capability to embed location data in the pictures, producing geocoded photographs.

The iPhone 3GS has a 3.2 megapixel camera, manufactured by OmniVision, featuring autofocus, auto white balance, and auto macro (up to 10 cm). It is also capable of capturing 640x480 (VGA resolution) video at 30 frames per second, although compared to higher-end CCD based video cameras it does exhibit the rolling shutter effect. The video can then be cropped on the device itself and directly uploaded to YouTube, MobileMe, or other services

The iPhone 4 introduced a 5.0 megapixel camera (2592x1936 pixels), also located on the back, which is equipped with a backside illuminated sensor capable of capturing pictures in low-light conditions, as well as an LED flash capable of staying lit for video recording at 720p resolution, considered high-definition. iPhone 4 is the first iPhone that has the high dynamic range photography feature. In addition the iPhone 4 has a second camera on the front capable ofVGA photos and SD video recording.

Regardless of the source, saved recordings may be synced to the host computer, attached to email, or (where supported) sent by MMS. Videos may be uploaded to YouTube directly.

The camera on the iPhone 4S is capable of shooting 8MP stills and record 1080p videos. The camera can now be accessed directly from the lock screen, and the volume up button as a shutter trigger. The built-in gyroscope is able to stabilize the camera while recording video.

Beta code pulled from iOS 5 suggests that the next feature to be released will allow users to capture a panoramic photo on their iPhone.

On all five model generations, the phone can be configured to bring up the camera app by quickly pressing the home key twice. On all iPhones running iOS 5 it can also be accessed from the lock screen directly. GB. On September 5, 2007, Apple discontinued the 4 GB models.On February 5, 2008, Apple added a 16 GB model. The iPhone 3G was available in 16 GB and 8 GB. The iPhone 3GS came in 16 GB and 32 GB variants and still is available in 8 GB. The iPhone 4 is available in 16 GB and 32 GB variants, as well as a newly introduced 8 GB variant to be sold along side the iPhone 4S at a reduced price point. The iPhone 4S is available in three sizes: 16 GB, 32 GB and 64 GB. All data is stored on the internal flash drive; the iPhone does not support expanded storage through a memory card slot, or the SIM card.

GSM Models of the iPhone use a SIM card to identify themselves to the GSM network. The SIM sits in a tray, which is inserted into a slot at the top of the device. The SIM tray can be ejected with a paperclip or the "SIM eject tool" (a simple piece of die-cut sheet metal) included with the iPhone 3G and 3GS. In most countries, the iPhone is usually sold with a SIM lock, which prevents the iPhone from being used on a different mobile network.

The GSM iPhone 4 features a MicroSIM card that is located in a slot on the right side of the device.

The CDMA model of the iPhone, like all CDMA phones, does not use a SIM.

The iPhone is equipped with liquid contact indicators which change from white to red in color when they come in contact with water. These suggest whether water damage has affected the device. The indicators on the iPhone include a small disc which is located at the bottom of the headphone jack and with the iPhone 3G and all later models an additional one is located at the bottom of the dock connector. The indicators are often used by Apple employees to determine whether the device qualifies for a warranty repair or replacement. If the indicators show that the device was exposed to water, they may determine that the device is not covered by Apple. However, the liquid contact indicators may be triggered through routine use, and if a device is worn while exercising, the sweat from an owner may dampen the indicators enough to indicate water damage. On many other mobile phones from different manufacturers, the liquid contact indicators are located in a protected location, such as beneath the battery behind a battery cover, but the indicators on an iPhone are directly exposed to the environment. This has led to criticism of the placement of the indicators, which may also be affected by steam in a bathroom or other light environmental moisture. In response to these criticisms, Apple made a silent change to their water damage policy for iPhones and similar products. This new policy allows the customer to request further internal inspection of the phone to verify if internal liquid damage sensors were triggered. 

All iPhone models include written documentation, and a dock connector to USB cable. The original and 3G iPhones also came with a cleaning cloth. The original iPhone included stereo headset (earbuds and a microphone) and a plastic dock to hold the unit upright while charging and syncing. The iPhone 3G includes a similar headset plus a SIM eject tool (the original model requires a paperclip). The iPhone 3GS includes the SIM eject tool and a revised headset, which adds volume buttons (not functional with previous iPhone versions). The iPhone 3G and 3GS are compatible with the same dock, sold separately, but not the original model's dock. All versions include a USB power adapter, or "wall charger," which allows the iPhone to charge from an AC outlet. The iPhone 3G and iPhone 3GS sold in North America, Japan, Colombia, Ecuador, or Peru include an ultracompact USB power adapter.

The iPhone, iPod Touch and iPad run an operating system known as iOS (formerly iPhone OS). It is a variant of the same Darwin operating system core that is found in Mac OS X. Also included is the "Core Animation" software component from Mac OS X v10.5 Leopard. Together with the PowerVR hardware (and on the iPhone 3GS, OpenGL ES 2.0), it is responsible for the interface's motion graphics. The operating system takes up less than half a gigabyte. It is capable of supporting bundled and future applications from Apple, as well as from third-party developers. Software applications cannot be copied directly from Mac OS X but must be written and compiled specifically for iOS.

Like the iPod, the iPhone is managed from a computer using iTunes. The earliest versions of the OS required version 7.3 or later, which is compatible with Mac OS X version 10.3.9 Panther or later, and 32-bit Windows XP or Vista. The release of iTunes 7.6 expanded this support to include 64-bit versions of XP and Vista, and a workaround has been discovered for previous 64-bit Windows operating systems. Apple provides free updates to the OS for the iPhone through iTunes, and major updates have historically accompanied new models. Such updates often require a newer version of iTunes — for example, the 3.0 update requires iTunes 8.2 — but the iTunes system requirements have stayed the same. Updates include both security patches and new features. For example, iPhone 3G users initially experienced dropped calls until an update was issued.

The interface is based around the home screen, a graphical list of available applications. iPhone applications normally run one at a time (not including iOS 4, which includes running applications in the background), although most functionality is still available when making a call or listening to music. The home screen can be accessed at any time by a hardware button below the screen, closing the open application in the process. By default, the Home screen contains the following icons: Messages (SMS and MMS messaging), Calendar, Photos, Camera, YouTube, Stocks, Maps (Google Maps), Weather, Voice Memos, Notes, Clock, Calculator, Settings, iTunes (store), App Store, and (on the iPhone 3GS and iPhone 4) Compass. Docked at the base of the screen, four icons for Phone, Mail, Safari(Internet), and iPod (multimedia) delineate the iPhone's main purposes. On January 15, 2008, Apple released software update 1.1.3, allowing users to create "Web Clips", home screen icons that resemble apps that open a user-defined page in Safari. After the update, iPhone users can rearrange and place icons on up to nine other adjacent home screens, accessed by a horizontal swipe. Users can also add and delete icons from the dock, which is the same on every home screen. Each home screen holds up to sixteen icons, and the dock holds up to four icons. Users can delete Web Clips and third-party applications at any time, and may select only certain applications for transfer from iTunes. Apple's default programs, however, may not be removed. The 3.0 update adds a system-wide search, known as Spotlight, to the left of the first home screen.

Almost all input is given through the touch screen, which understands complex gestures using multi-touch. The iPhone's interaction techniques enable the user to move the content up or down by a touch-drag motion of the finger. For example, zooming in and out of web pages and photos is done by placing two fingers on the screen and spreading them farther apart or bringing them closer together, a gesture known as "pinching". Scrolling through a long list or menu is achieved by sliding a finger over the display from bottom to top, or vice versa to go back. In either case, the list moves as if it is pasted on the outer surface of a wheel, slowly decelerating as if affected by friction. In this way, the interface simulates the physics of a real object. Other user-centered interactive effects include horizontally sliding sub-selection, the vertically sliding keyboard and bookmarks menu, and widgets that turn around to allow settings to be configured on the other side. Menu bars are found at the top and bottom of the screen when necessary. Their options vary by program, but always follow a consistent style motif. In menu hierarchies, a "back" button in the top-left corner of the screen displays the name of the parent folder.

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