An application shell is the minimal HTML, CSS, and JavaScript powering a user interface. The application shell should:
- load fast
- be cached
- dynamically display content
An application shell is the secret to reliably good performance. Think of your app's shell like the bundle of code you'd publish to an app store if you were building a native app. It's the load needed to get off the ground, but might not be the whole story. It keeps your UI local and pulls in content dynamically through an API.
https://developers.google.com/web/progressive-web-apps/checklist
To test locally:
python -m SimpleHTTPServer 8000