A
graphical user interface builder (or
GUI builder), also known as
GUI designer, is a
software development tool that simplifies the creation of
GUIs by allowing the designer to arrange
graphical control elements (often called widgets) using a
drag-and-drop WYSIWYG editor. Without a GUI builder, a GUI must be built by manually specifying each widget's parameters in source-code, with no visual feedback until the program is run.