| Phonon::BackendCapabilities | Contains functions to describe the capabilities of the multimedia backend |
| Phonon | Contains classes and functions for multimedia applications |
| QDBus | Contains miscellaneous identifiers used throughout the QtDBus library |
| QGL | Specifies miscellaneous identifiers used in the Qt OpenGL module |
| QSql | Contains miscellaneous identifiers used throughout the Qt SQL library |
| QSsl | Declares enums common to all SSL classes in QtNetwork |
| QTest | Contains all the functions and declarations that are related to the QTestLib tool |
| Qt | Contains miscellaneous identifiers used throughout the Qt library |
| QtConcurrent | High-level APIs that make it possible to write multi-threaded programs without using low-level threading primitives |