These classes are useful classes not fitting into any other category.
| QDoubleValidator | Range checking of floating-point numbers |
| QErrorMessage | Error message display dialog |
| QIntValidator | Validator that ensures a string contains a valid integer within a specified range |
| QKeySequence | Encapsulates a key sequence as used by shortcuts |
| QLibraryInfo | Information about the Qt library |
| QMacMime | Maps open-standard MIME to Mac flavors |
| QProcess | Used to start external programs and to communicate with them |
| QRegExp | Pattern matching using regular expressions |
| QRegExpValidator | Used to check a string against a regular expression |
| QRubberBand | Rectangle or line that can indicate a selection or a boundary |
| QSettings | Persistent platform-independent application settings |
| QSharedData | Base class for shared data objects |
| QSharedDataPointer | Pointer to a shared data object |
| QSplashScreen | Splash screen that can be shown during application startup |
| QUrl | Convenient interface for working with URLs |
| QUrlInfo | Stores information about URLs |
| QUuid | Stores a Universally Unique Identifier (UUID) |
| QValidator | Validation of input text |
| QVariant | Acts like a union for the most common Qt data types |
| QWindowsMime | Maps open-standard MIME to Window Clipboard formats |
| Qt | Miscellaneous identifiers used throughout the Qt library |
