The Standard Widget Toolkit (SWT) is a widget toolkit for Java developers that provides a portable API and tight integration with the underlying native OS GUI platform.
Many low level UI programming tasks are handled in higher layers of the Eclipse platform. For example, JFace viewers and actions provide implementations for the common interactions between applications and widgets. However, knowledge of SWT is important for understanding how the rest of the platform works.
SWT defines a common portable API that is provided on all supported platforms, and implements the API on each platform using native widgets wherever possible. This allows the toolkit to immediately reflect any changes in the underlying OS GUI look and feel while maintaining a consistent programming model on all platforms.