UIQ (formerly known as User Interface Quartz) by UIQ Technology is a software platform based upon Symbian OS. Essentially this is a graphical user interface layer that provides additional components to the core OS, to enable the development of feature-rich mobile phones that are open to expanded capabilities through third-party applications.

Native applications can be written in C++ using the Symbian/UIQ SDK. All UIQ-based phones (2.x and 3.x) also support Java applications.

Version 2.x and 3.x are pen-based and used in the following 2.5G and 3G smartphones: Sony Ericsson P800/P900/P910/P990/M600/W950/P1/W960/G700/G900, BenQ P30/P31 and Arima U300/U308, Nokia 6708, Motorola A920/A925/A1000/M1000.

UIQ phones employ touch screens with a resolution of 208×320 pixels (UIQ 1.x & 2.x) and 240×320 (UIQ 3.x). Depending on the phone, the color depth is 12-bit (4096 colors), 16-bit (65536 colors), 18-bit (262144 colors), and 24-bit (16,777,216 colors) on some newer phones.

For developers the significant items are:

- Single SDK model - developers targeting core UIQ features can use the UIQ SDK to target any UIQ 3 device. Extensions targeting specific device features (such as WiFi, etc) are available from phone manufacturers websites.
- Increased tools support - developers can use whichever tools they are familiar with (DevStudio, Eclipse, Carbide, CodeWarrior, NetBeans). Many of these tools are beginning to support extensive RAD features for both C++ and Java developers. Visual Basic programmers can use NS Basic/Symbian OS.
- High volume, mid-range devices are now possible, to significantly increase the potential customer base.