This page describes how to use the web preview feature in Cloud Shell. This feature allows you to run web applications on the Cloud Shell virtual machine instance and preview them from the Google Cloud console.
The Web Preview button 
can be found on the top right of the Cloud Shell taskbar.
Start the web application
You can run any web application that listens to HTTP requests on the Cloud Shell virtual machine, including the App Engine development server. The web application must listen for HTTP requests on ports within the permitted range 2000 to 65000. These ports are only available to the secure Cloud Shell proxy service, which restricts access over HTTPS to your user account only.
Simple server example
To start a simple Python HTTP server from the Cloud Shell command prompt:
cd `mktemp -d` \
&& echo '<html><body>Hello World</body></html>' >./index.html \
&& python -m http.server 8080
App Engine development server example
To clone a sample App Engine application and run it on the App Engine development server:
git clone https://github.com/GoogleCloudPlatform/appengine-guestbook-python \
&& cd appengine-guestbook-python \
&& dev_appserver.py ./app.yaml
The development server runs on port 8080 by default.
Preview the application
Click the Web Preview button
and then select
the port number from the displayed menu. Cloud Shell opens the preview URL on
its proxy service in a new browser window.
You can also access the preview URL by combining the port with the environment
variable WEB_HOST in the Cloud Shell terminal using the format https://$PORT-$WEB_HOST,
or by using the Cloud Shell API.