Quickstart

Get up and running with Dear ImGui in minutes with a complete Hello World example

Overview

This guide will help you create your first Dear ImGui application. We’ll build a simple “Hello World” program that displays a window with some basic widgets.

This quickstart uses GLFW for windowing and OpenGL 3 for rendering, which work on Windows, macOS, and Linux. For other platforms or graphics APIs, see the Integration Guide.

Prerequisites

Before you begin, ensure you have:

• A C++ compiler (C++11 or later)
• GLFW library
• OpenGL 3.0+ support

Installation

1. Download Dear ImGui

   Clone or download Dear ImGui from GitHub:

   git clone https://github.com/ocornut/imgui.git
   cd imgui
   

   The core library files are:

   • imgui.cpp, imgui.h
   • imgui_demo.cpp
   • imgui_draw.cpp
   • imgui_tables.cpp
   • imgui_widgets.cpp
   • imconfig.h (configuration)
2. Get the backends

   For this quickstart, you’ll need:

   • backends/imgui_impl_glfw.cpp + imgui_impl_glfw.h (platform backend)
   • backends/imgui_impl_opengl3.cpp + imgui_impl_opengl3.h (renderer backend)
3. Install GLFW

   Ubuntu/Debian

   sudo apt-get install libglfw3-dev
   

   macOS

   brew install glfw
   

   Windows

   Download GLFW from glfw.org or use vcpkg:

   vcpkg install glfw3
   

Your First Dear ImGui Program

Create a file called main.cpp with the following code:

main.cpp

#include "imgui.h"
#include "imgui_impl_glfw.h"
#include "imgui_impl_opengl3.h"
#include <GLFW/glfw3.h>
#include <stdio.h>

int main(int, char**)
{
    // Initialize GLFW
    if (!glfwInit())
        return 1;

    // GL 3.0 + GLSL 130
    const char* glsl_version = "#version 130";
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);

    // Create window with graphics context
    GLFWwindow* window = glfwCreateWindow(1280, 720, "Dear ImGui - Hello World", nullptr, nullptr);
    if (window == nullptr)
        return 1;
    glfwMakeContextCurrent(window);
    glfwSwapInterval(1); // Enable vsync

    // Setup Dear ImGui context
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO();

    // Setup Dear ImGui style
    ImGui::StyleColorsDark();

    // Setup Platform/Renderer backends
    ImGui_ImplGlfw_InitForOpenGL(window, true);
    ImGui_ImplOpenGL3_Init(glsl_version);

    // Our state
    bool show_demo_window = true;
    bool show_another_window = false;
    ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);

    // Main loop
    while (!glfwWindowShouldClose(window))
    {
        glfwPollEvents();

        // Start the Dear ImGui frame
        ImGui_ImplOpenGL3_NewFrame();
        ImGui_ImplGlfw_NewFrame();
        ImGui::NewFrame();

        // 1. Show the big demo window (Most of the sample code is in ImGui::ShowDemoWindow()!)
        if (show_demo_window)
            ImGui::ShowDemoWindow(&show_demo_window);

        // 2. Show a simple window that we create ourselves
        {
            static float f = 0.0f;
            static int counter = 0;

            ImGui::Begin("Hello, World!");

            ImGui::Text("This is some useful text.");
            ImGui::Checkbox("Demo Window", &show_demo_window);
            ImGui::Checkbox("Another Window", &show_another_window);

            ImGui::SliderFloat("float", &f, 0.0f, 1.0f);
            ImGui::ColorEdit3("clear color", (float*)&clear_color);

            if (ImGui::Button("Button"))
                counter++;
            ImGui::SameLine();
            ImGui::Text("counter = %d", counter);

            ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 
                       1000.0f / io.Framerate, io.Framerate);
            ImGui::End();
        }

        // 3. Show another simple window
        if (show_another_window)
        {
            ImGui::Begin("Another Window", &show_another_window);
            ImGui::Text("Hello from another window!");
            if (ImGui::Button("Close Me"))
                show_another_window = false;
            ImGui::End();
        }

        // Rendering
        ImGui::Render();
        int display_w, display_h;
        glfwGetFramebufferSize(window, &display_w, &display_h);
        glViewport(0, 0, display_w, display_h);
        glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
        glClear(GL_COLOR_BUFFER_BIT);
        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());

        glfwSwapBuffers(window);
    }

    // Cleanup
    ImGui_ImplOpenGL3_Shutdown();
    ImGui_ImplGlfw_Shutdown();
    ImGui::DestroyContext();

    glfwDestroyWindow(window);
    glfwTerminate();

    return 0;
}

Building Your Application

g++ / Clang

g++ -std=c++11 main.cpp \
    imgui/imgui*.cpp \
    imgui/backends/imgui_impl_glfw.cpp \
    imgui/backends/imgui_impl_opengl3.cpp \
    -I imgui -I imgui/backends \
    -lglfw -lGL -ldl \
    -o hello_imgui

CMake

Create a CMakeLists.txt:

cmake_minimum_required(VERSION 3.10)
project(HelloImGui)

set(CMAKE_CXX_STANDARD 11)

find_package(OpenGL REQUIRED)
find_package(glfw3 REQUIRED)

add_executable(hello_imgui
    main.cpp
    imgui/imgui.cpp
    imgui/imgui_demo.cpp
    imgui/imgui_draw.cpp
    imgui/imgui_tables.cpp
    imgui/imgui_widgets.cpp
    imgui/backends/imgui_impl_glfw.cpp
    imgui/backends/imgui_impl_opengl3.cpp
)

target_include_directories(hello_imgui PRIVATE imgui imgui/backends)
target_link_libraries(hello_imgui OpenGL::GL glfw)

Build with:

mkdir build && cd build
cmake ..
make

Visual Studio

1. Create a new C++ Console Application
2. Add all Dear ImGui source files to your project:
   • Core: imgui*.cpp files
   • Backends: imgui_impl_glfw.cpp, imgui_impl_opengl3.cpp
3. Add include directories: imgui/ and imgui/backends/
4. Link against: opengl32.lib, glfw3.lib
5. Build and run (F5)

Run Your Application

Execute your compiled program:

./hello_imgui

You should see a window with:

• A demo window showcasing Dear ImGui features
• A “Hello, World!” window with a slider, color picker, and button
• Smooth 60 FPS rendering

Press Ctrl+Click on any slider to type in a value directly!

Understanding the Code

Let’s break down the key parts:

Initialization

// Setup Dear ImGui context
IMGUI_CHECKVERSION();
ImGui::CreateContext();
ImGuiIO& io = ImGui::GetIO();

• IMGUI_CHECKVERSION() ensures your headers match the compiled library
• CreateContext() initializes Dear ImGui’s internal state
• GetIO() provides access to input/output configuration

Frame Loop

ImGui_ImplOpenGL3_NewFrame();
ImGui_ImplGlfw_NewFrame();
ImGui::NewFrame();

// Your UI code here

ImGui::Render();
ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());

Every frame follows this pattern:

1. Start a new Dear ImGui frame
2. Create your UI with ImGui calls
3. Render the draw data

Creating UI

ImGui::Begin("Hello, World!");
ImGui::Text("This is some useful text.");
ImGui::Checkbox("Demo Window", &show_demo_window);
ImGui::SliderFloat("float", &f, 0.0f, 1.0f);
if (ImGui::Button("Button"))
    counter++;
ImGui::End();

Dear ImGui functions return values when interaction happens:

• Button() returns true when clicked
• Checkbox() modifies the bool and returns true when changed
• Begin() / End() define a window scope

Next Steps

Integration Guide

Learn how to integrate Dear ImGui into your existing project

Core Concepts

Understand the immediate mode paradigm

Widgets Overview

Explore all available widgets

Examples

Browse 30+ complete example applications

Common Issues

Blank window / Nothing renders

Make sure you’re calling:

1. ImGui::NewFrame() at the start of each frame
2. ImGui::Render() after your UI code
3. ImGui_ImplXXX_RenderDrawData(ImGui::GetDrawData()) to draw

Assertion failed: IMGUI_CHECKVERSION()

Your headers don’t match the compiled version. Make sure all Dear ImGui files are from the same version.

Missing fonts / Square boxes instead of text

The font texture wasn’t uploaded. Most backends handle this automatically, but you may need to call ImGui_ImplXXX_CreateFontsTexture().

ImGui::Begin() not returning false when collapsed

Always call ImGui::End() regardless of the return value from Begin(). This is a common beginner mistake.

Explore the full Demo Window (ImGui::ShowDemoWindow()) to see all features in action with interactive examples and code snippets!