Learn Qt-webassembly - 9 Code Examples & CST Typing Practice Test

Qt for WebAssembly allows developers to build Qt applications that run directly in web browsers using WebAssembly, without the need for plugins. It enables rich, cross-platform GUI apps to execute in modern browsers efficiently.

View all 9 Qt-webassembly code examples →

Qt WebAssembly Counter Example Qt WebAssembly Hello World Qt WebAssembly Button Click Example Qt WebAssembly Text Input Example Qt WebAssembly Slider Example Qt WebAssembly Toggle Button Example Qt WebAssembly Color Change Example Qt WebAssembly Checkbox Example Qt WebAssembly Progress Bar Example

Learn QT-WEBASSEMBLY with Real Code Examples

Updated Nov 25, 2025

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Code Sample Descriptions

Qt WebAssembly Counter Example

#include <QApplication>
#include <QWidget>
#include <QPushButton>
#include <QLabel>
#include <QVBoxLayout>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Qt WebAssembly Counter");

    int count = 0;
    QLabel *label = new QLabel(QString("Counter: %1").arg(count));
    QPushButton *btnIncrement = new QPushButton("+");
    QPushButton *btnDecrement = new QPushButton("-");
    QPushButton *btnReset = new QPushButton("Reset");

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(label);
    layout->addWidget(btnIncrement);
    layout->addWidget(btnDecrement);
    layout->addWidget(btnReset);
    window.setLayout(layout);

    QObject::connect(btnIncrement, &QPushButton::clicked, [&](){
        count++;
        label->setText(QString("Counter: %1").arg(count));
    });

    QObject::connect(btnDecrement, &QPushButton::clicked, [&](){
        count--;
        label->setText(QString("Counter: %1").arg(count));
    });

    QObject::connect(btnReset, &QPushButton::clicked, [&](){
        count = 0;
        label->setText(QString("Counter: %1").arg(count));
    });

    window.show();
    return app.exec();
}

Demonstrates a simple counter layout using Qt Widgets and C++ compiled to WebAssembly for browser interactivity.

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Qt WebAssembly Hello World

#include <QApplication>
#include <QWidget>
#include <QLabel>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Hello Qt WebAssembly");

    QLabel *label = new QLabel("Hello, WebAssembly!");
    label->setAlignment(Qt::AlignCenter);

    window.setFixedSize(300, 200);
    label->setParent(&window);
    window.show();
    return app.exec();
}

Displays a simple 'Hello World' label in a Qt WebAssembly browser app.

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Qt WebAssembly Button Click Example

#include <QApplication>
#include <QWidget>
#include <QPushButton>
#include <QLabel>
#include <QVBoxLayout>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Button Click Example");

    QLabel *label = new QLabel("Button not clicked");
    QPushButton *button = new QPushButton("Click Me");

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(label);
    layout->addWidget(button);
    window.setLayout(layout);

    QObject::connect(button, &QPushButton::clicked, [&](){
        label->setText("Button Clicked!");
    });

    window.show();
    return app.exec();
}

A simple button click event example for Qt WebAssembly.

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Qt WebAssembly Text Input Example

#include <QApplication>
#include <QWidget>
#include <QLineEdit>
#include <QLabel>
#include <QVBoxLayout>
#include <QString>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Text Input Example");

    QLineEdit *lineEdit = new QLineEdit();
    QLabel *label = new QLabel("Enter text above");

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(lineEdit);
    layout->addWidget(label);
    window.setLayout(layout);

    QObject::connect(lineEdit, &QLineEdit::textChanged, [&](const QString &text){
        label->setText("You typed: " + text);
    });

    window.show();
    return app.exec();
}

Captures user input from a text box and displays it.

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Qt WebAssembly Slider Example

#include <QApplication>
#include <QWidget>
#include <QSlider>
#include <QLabel>
#include <QVBoxLayout>
#include <Qt>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Slider Example");

    QLabel *label = new QLabel("Value: 0");
    QSlider *slider = new QSlider(Qt::Horizontal);
    slider->setRange(0, 100);

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(label);
    layout->addWidget(slider);
    window.setLayout(layout);

    QObject::connect(slider, &QSlider::valueChanged, [&](int value){
        label->setText("Value: " + QString::number(value));
    });

    window.show();
    return app.exec();
}

Demonstrates a slider controlling a label value.

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Qt WebAssembly Toggle Button Example

#include <QApplication>
#include <QWidget>
#include <QPushButton>
#include <QVBoxLayout>
#include <QString>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Toggle Button Example");

    QPushButton *button = new QPushButton("OFF");
    QVBoxLayout *layout = new QVBoxLayout();
    layout->addWidget(button);
    window.setLayout(layout);

    QObject::connect(button, &QPushButton::clicked, [=]() mutable {
        if(button->text() == "OFF") button->setText("ON");
        else button->setText("OFF");
    });

    window.show();
    return app.exec();
}

A toggle button changes the text between ON and OFF.

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Qt WebAssembly Color Change Example

#include <QApplication>
#include <QWidget>
#include <QPushButton>
#include <QLabel>
#include <QVBoxLayout>
#include <QPalette>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Color Change Example");

    QLabel *label = new QLabel("Watch my color");
    QPushButton *button = new QPushButton("Change Color");

    QVBoxLayout *layout = new QVBoxLayout();
    layout->addWidget(label);
    layout->addWidget(button);
    window.setLayout(layout);

    QObject::connect(button, &QPushButton::clicked, [=]() {
        QPalette pal = label->palette();
        pal.setColor(QPalette::WindowText, Qt::red);
        label->setPalette(pal);
    });

    window.show();
    return app.exec();
}

Changes label color on button click.

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Qt WebAssembly Checkbox Example

#include <QApplication>
#include <QWidget>
#include <QCheckBox>
#include <QLabel>
#include <QVBoxLayout>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Checkbox Example");

    QCheckBox *checkBox = new QCheckBox("Check me");
    QLabel *label = new QLabel("Unchecked");

    QVBoxLayout *layout = new QVBoxLayout();
    layout->addWidget(checkBox);
    layout->addWidget(label);
    window.setLayout(layout);

    QObject::connect(checkBox, &QCheckBox::stateChanged, [&](int state){
        label->setText(state == Qt::Checked ? "Checked" : "Unchecked");
    });

    window.show();
    return app.exec();
}

A checkbox toggles a label between checked and unchecked.

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Qt WebAssembly Progress Bar Example

#include <QApplication>
#include <QWidget>
#include <QSlider>
#include <QProgressBar>
#include <QVBoxLayout>
#include <Qt>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Progress Bar Example");

    QSlider *slider = new QSlider(Qt::Horizontal);
    QProgressBar *progress = new QProgressBar();
    slider->setRange(0, 100);
    progress->setRange(0, 100);

    QVBoxLayout *layout = new QVBoxLayout();
    layout->addWidget(slider);
    layout->addWidget(progress);
    window.setLayout(layout);

    QObject::connect(slider, &QSlider::valueChanged, [&](int value){
        progress->setValue(value);
    });

    window.show();
    return app.exec();
}

Updates a progress bar based on a slider value.

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Frequently Asked Questions about Qt-webassembly

What is Qt-webassembly?

What are the primary use cases for Qt-webassembly?

Porting existing Qt desktop apps to web browsers. Building interactive web applications with Qt Quick. Creating browser-based prototypes without rewriting in JavaScript/HTML. Developing cross-platform enterprise GUI apps. Deploying games or simulation tools in browsers

What are the strengths of Qt-webassembly?

Cross-platform deployment from single C++ codebase. Near-native performance in browsers. Rich GUI capabilities (Qt Widgets & Qt Quick). Leverages mature Qt ecosystem. Supports offline operation via IndexedDB/localStorage

What are the limitations of Qt-webassembly?

Limited access to some native OS features. Application size can be large due to Qt runtime. Debugging in browser can be more complex. Performance depends on browser WASM optimizations. Requires Emscripten toolchain and modern browser support

How can I practice Qt-webassembly typing speed?

CodeSpeedTest offers 9+ real Qt-webassembly code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.

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Code Sample Descriptions

Qt WebAssembly Counter Example

#include <QApplication>
#include <QWidget>
#include <QPushButton>
#include <QLabel>
#include <QVBoxLayout>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Qt WebAssembly Counter");

    int count = 0;
    QLabel *label = new QLabel(QString("Counter: %1").arg(count));
    QPushButton *btnIncrement = new QPushButton("+");
    QPushButton *btnDecrement = new QPushButton("-");
    QPushButton *btnReset = new QPushButton("Reset");

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(label);
    layout->addWidget(btnIncrement);
    layout->addWidget(btnDecrement);
    layout->addWidget(btnReset);
    window.setLayout(layout);

    QObject::connect(btnIncrement, &QPushButton::clicked, [&](){
        count++;
        label->setText(QString("Counter: %1").arg(count));
    });

    QObject::connect(btnDecrement, &QPushButton::clicked, [&](){
        count--;
        label->setText(QString("Counter: %1").arg(count));
    });

    QObject::connect(btnReset, &QPushButton::clicked, [&](){
        count = 0;
        label->setText(QString("Counter: %1").arg(count));
    });

    window.show();
    return app.exec();
}

Demonstrates a simple counter layout using Qt Widgets and C++ compiled to WebAssembly for browser interactivity.

Let’s Try →

Qt WebAssembly Hello World

#include <QApplication>
#include <QWidget>
#include <QLabel>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Hello Qt WebAssembly");

    QLabel *label = new QLabel("Hello, WebAssembly!");
    label->setAlignment(Qt::AlignCenter);

    window.setFixedSize(300, 200);
    label->setParent(&window);
    window.show();
    return app.exec();
}

Displays a simple 'Hello World' label in a Qt WebAssembly browser app.

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Qt WebAssembly Button Click Example

#include <QApplication>
#include <QWidget>
#include <QPushButton>
#include <QLabel>
#include <QVBoxLayout>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Button Click Example");

    QLabel *label = new QLabel("Button not clicked");
    QPushButton *button = new QPushButton("Click Me");

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(label);
    layout->addWidget(button);
    window.setLayout(layout);

    QObject::connect(button, &QPushButton::clicked, [&](){
        label->setText("Button Clicked!");
    });

    window.show();
    return app.exec();
}

A simple button click event example for Qt WebAssembly.

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Qt WebAssembly Text Input Example

#include <QApplication>
#include <QWidget>
#include <QLineEdit>
#include <QLabel>
#include <QVBoxLayout>
#include <QString>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Text Input Example");

    QLineEdit *lineEdit = new QLineEdit();
    QLabel *label = new QLabel("Enter text above");

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(lineEdit);
    layout->addWidget(label);
    window.setLayout(layout);

    QObject::connect(lineEdit, &QLineEdit::textChanged, [&](const QString &text){
        label->setText("You typed: " + text);
    });

    window.show();
    return app.exec();
}

Captures user input from a text box and displays it.

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Qt WebAssembly Slider Example

#include <QApplication>
#include <QWidget>
#include <QSlider>
#include <QLabel>
#include <QVBoxLayout>
#include <Qt>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Slider Example");

    QLabel *label = new QLabel("Value: 0");
    QSlider *slider = new QSlider(Qt::Horizontal);
    slider->setRange(0, 100);

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(label);
    layout->addWidget(slider);
    window.setLayout(layout);

    QObject::connect(slider, &QSlider::valueChanged, [&](int value){
        label->setText("Value: " + QString::number(value));
    });

    window.show();
    return app.exec();
}

Demonstrates a slider controlling a label value.

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Qt WebAssembly Toggle Button Example

#include <QApplication>
#include <QWidget>
#include <QPushButton>
#include <QVBoxLayout>
#include <QString>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Toggle Button Example");

    QPushButton *button = new QPushButton("OFF");
    QVBoxLayout *layout = new QVBoxLayout();
    layout->addWidget(button);
    window.setLayout(layout);

    QObject::connect(button, &QPushButton::clicked, [=]() mutable {
        if(button->text() == "OFF") button->setText("ON");
        else button->setText("OFF");
    });

    window.show();
    return app.exec();
}

A toggle button changes the text between ON and OFF.

Let’s Try →

Qt WebAssembly Color Change Example

#include <QApplication>
#include <QWidget>
#include <QPushButton>
#include <QLabel>
#include <QVBoxLayout>
#include <QPalette>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Color Change Example");

    QLabel *label = new QLabel("Watch my color");
    QPushButton *button = new QPushButton("Change Color");

    QVBoxLayout *layout = new QVBoxLayout();
    layout->addWidget(label);
    layout->addWidget(button);
    window.setLayout(layout);

    QObject::connect(button, &QPushButton::clicked, [=]() {
        QPalette pal = label->palette();
        pal.setColor(QPalette::WindowText, Qt::red);
        label->setPalette(pal);
    });

    window.show();
    return app.exec();
}

Changes label color on button click.

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Qt WebAssembly Checkbox Example

#include <QApplication>
#include <QWidget>
#include <QCheckBox>
#include <QLabel>
#include <QVBoxLayout>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Checkbox Example");

    QCheckBox *checkBox = new QCheckBox("Check me");
    QLabel *label = new QLabel("Unchecked");

    QVBoxLayout *layout = new QVBoxLayout();
    layout->addWidget(checkBox);
    layout->addWidget(label);
    window.setLayout(layout);

    QObject::connect(checkBox, &QCheckBox::stateChanged, [&](int state){
        label->setText(state == Qt::Checked ? "Checked" : "Unchecked");
    });

    window.show();
    return app.exec();
}

A checkbox toggles a label between checked and unchecked.

Let’s Try →

Qt WebAssembly Progress Bar Example

#include <QApplication>
#include <QWidget>
#include <QSlider>
#include <QProgressBar>
#include <QVBoxLayout>
#include <Qt>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QWidget window;
    window.setWindowTitle("Progress Bar Example");

    QSlider *slider = new QSlider(Qt::Horizontal);
    QProgressBar *progress = new QProgressBar();
    slider->setRange(0, 100);
    progress->setRange(0, 100);

    QVBoxLayout *layout = new QVBoxLayout();
    layout->addWidget(slider);
    layout->addWidget(progress);
    window.setLayout(layout);

    QObject::connect(slider, &QSlider::valueChanged, [&](int value){
        progress->setValue(value);
    });

    window.show();
    return app.exec();
}

Updates a progress bar based on a slider value.

Let’s Try →

Frequently Asked Questions about Qt-webassembly

What is Qt-webassembly?

What are the primary use cases for Qt-webassembly?

What are the strengths of Qt-webassembly?

What are the limitations of Qt-webassembly?

How can I practice Qt-webassembly typing speed?

CodeSpeedTest offers 9+ real Qt-webassembly code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.