It was 116 millimetres (4.6 in) high, 62 millimetres (2.4 in) wide, and 12 millimetres (0.47 in) deep, compared to its predecessor, which was 110 millimetres (4.3 in) high, 61 millimetres (2.4 in) wide, and 12 millimetres (0.47 in) deep.
The i Phone 3G sported a 3.5 in (89 mm) capacitive touchscreen with a 480×320 (HVGA) resolution at 163 ppi.
The i Phone 3G's back featured a redesigned polycarbonate plastic housing, replacing the aluminum back of the first generation.
Buttons were changed from plastic to metal, and the edges of the phone were tapered, providing a better grip.
This introduced the App Store, Microsoft Exchange Active Sync support, Apple’s Mobile Me service, and push email support, along with other new features and bug fixes.
In June 2009, i Phone 3G users received the i Phone OS 3.0 software update, which introduced the long-awaited MMS feature, copy and paste, landscape support for more applications, Bluetooth stereo support, and other improvements.
The i Phone 3G is internally similar to its predecessor, but included several new hardware features, such as GPS, 3G data and tri-band UMTS/HSDPA.
This update was widely criticized for slow performance on i Phone 3G, though September 2010's i OS 4.1 release resolved this problem.
The device featured the same sensors as its predecessor.
The proximity sensor (which deactivates the display during calls when the face is near) was repositioned to save battery power and to prevent inadvertent inputs from the user’s face and ears.
An ambient light sensor was included to adjust the display brightness for different lighting conditions, which helps save battery power.
A 3-axis accelerometer was included to sense the orientation of the phone and change the screen accordingly, allowing the user to easily switch between portrait and landscape mode.
However, the i Phone 3G is unable to use many features included in this update, such as Air Play and Safari Text Search.