The iPhone was initially released with two options for internal storage size: 4 GB or 8 GB. On September 5, 2007, Apple discontinued the 4 GB models.[61] On February 5, 2008, Apple added a 16 GB model.[62] 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. 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.

The SIM card 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.[63][64] In most countries, the iPhone is usually sold with a SIM lock, which prevents the iPhone from being used on a different mobile network.[65]

The iPhone 4 features a MicroSIM card that is located in a slot on the right side of the device.[66]