Introduced Windows Vista support, introduced native CSS support for widget styling, as well as the QGraphicsView framework for efficient rendering of thousands of 2D objects onscreen, to replace Qt 3.x's QCanvas class.
Features included are improved multimedia support using Phonon, enhanced XML support, a concurrency framework to ease developing multi-threaded applications, an IPC framework with a focus on shared memory, and WebKit integration.
Major included features are QtCreator, improved graphical engine, improved integration with WebKit, OpenDocument Format write support and new licensing options, as well as OS X Cocoa framework support.
New APIs are Framework Animation, Gestures, Multi-touch. Now supports (as Tier 1) Symbian and (as Tier 2) Windows 7 and Mac OS X 10.6, support extended for some Unix systems. Improvements have also been made to overall performance.
Framework development of Qt 5 moved to open governance, taking place at qt-project.org. It is now possible for developers outside Nokia/Digia to submit patches and have them reviewed.