<!-- Deleted image removed: -->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 widgets using a drag-and-dropWYSIWYG editor. Without a GUI builder, a GUI must be built by manually specifying each widget's parameters in code, with no visual feedback until the program is run.
User interfaces are commonly programmed using an event-driven architecture, so GUI builders also simplify creating event-driven code. This supporting code connects widgets with the outgoing and incoming events that trigger the functions providing the application logic.