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 in your environment. Then you can make your application appear in a web browser by pointing it at 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, broadwayd, that ships with GTK. To use broadwayd, start it like this:

broadwayd :5

Then point your web browser at Start your applications like this:

GDK_BACKEND=broadway BROADWAY_DISPLAY=:5 gtk3-demo

Broadway-specific environment variables

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