A graphical user interface builder (or GUI builder), also known as GUI designer or sometimes rapid application development (RAD) integrated development environment (IDE), is a software development tool that simplifies creating graphical user interfaces (GUIs) by allowing a 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 the source 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 software widgets with the outgoing and incoming events that trigger the functions providing the application logic.
Some graphical user interface builders automatically generate all the source code for a graphical control element. Others, like Interface Builder or Glade Interface Designer, generate serialized object instances that are then loaded by the application.

List of GUI builders

C language based
GTK, Glade Interface Designer
Motif
XForms (toolkit) fdesign
Intrinsics

C# based
UWP, Windows Presentation Foundation, WinForms
Microsoft Visual Studio XAML Editor, XAML based GUI layout
Microsoft Expression Blend
SharpDevelop
Xamarin.Forms, .NET
Xamarin Studio

C++ based
UWP, Windows Presentation Foundation, WinForms
Microsoft Visual Studio XAML Editor, XAML based GUI layout
Microsoft Blend
Qt (software)
Qt Creator
FLTK
FLUID
JUCE
U++
wxWidgets
wxFormBuilder

Objective-C, Swift based
Cocoa (modern, formerly OpenStep) and Carbon (deprecated).
Xcode
GNUstep
Gorm

Java based
Android Studio, XML-based GUI layout
NetBeans GUI design tool

HTML–JavaScript based
Adobe Dreamweaver

Python based

Object Pascal based
Delphi, Visual Component Library (VCL)
Lazarus, Lazarus Component Library (LCL)

Tk framework based
Tk (software) for Tcl
Komodo Edit (No longer has a GUI builder)

Visual Basic based
UWP, Windows Presentation Foundation, WinForms
Microsoft Visual Studio XAML Editor, XAML based GUI layout
Microsoft Expression Blend

Other tools
Adobe Animate
App Inventor for Android
AutoIt
Creately
Embedded Wizard
GEM
Interface Builder
LucidChart
OpenWindows
Resource construction set
Stetic
Scaleform
Wavemaker

List of development environments

IDEs with GUI builders (RAD IDEs)
4D
Komodo Edit (No longer has a GUI builder)
Android Studio
Anjuta
AutoIt3
C++Builder
Clarion
Code::Blocks
CodeLite
dBase
Delphi/RAD Studio
Embedded Wizard
Eclipse
Gambas
IntelliJ IDEA
InForm
JDeveloper
KDevelop
LabWindows/CVI
LANSA
Lazarus
Liberty BASIC
Microsoft Visual Studio
MonoDevelop
MSEide+MSEgui
MyEclipse
NetBeans
OutSystems
PascalABC.NET
Projucer
Purebasic
Qt Creator
SharpDevelop
Softwell Maker
U++
VB6
WinFBE
Xcode
Xojo

See also
Model–view–controller
Web template system
Rapid application development (RAD)
Human interface guidelines (HIG)
Human interface device
User interface markup language
User interface modeling
Linux on the desktop

References