gtk2/docs/reference/gtk/broadway.md

Title: The Broadway windowing system
Slug: broadway

## Using GTK with Broadway

The GDK Broadway backend provides support for displaying GTK applications in
a web browser, using HTML5 and web sockets.

To run your application in this way, select the Broadway backend by setting
`GDK_BACKEND=broadway`. Then you can make your application appear in a web
browser by pointing it at `http://127.0.0.1:8080`. Note that you need to
enable web sockets in your web browser.

You can choose a different port from the default 8080 by setting the
`BROADWAY_DISPLAY` environment variable to the port that you want to use.

It is also possible to use multiple GTK applications in the same web browser
window, by using the Broadway server, `gtk4-broadwayd`, that ships with GTK.
To start the Broadway server use:

```
gtk4-broadwayd :5
```

Then point your web browser at `http://127.0.0.1:8085`.

Once the Broadway server is running, you can start your applications like
this:

```
GDK_BACKEND=broadway BROADWAY_DISPLAY=:5 gtk4-demo
```

## Broadway-specific environment variables

### `BROADWAY_DISPLAY`

Specifies the Broadway display number. The default display is 0.

The display number determines the port to use when connecting to a Broadway
application via the following formula:

```
port = 8080 + display
```