start_url does not respond with a 200 when offline

The manifest for a Progressive Web App (PWA) should include a start_url, which indicates the URL to be loaded when the user launches the app.

If the browser doesn't receive an HTTP 200 response when accessing an app from the start_url, either the start_url isn't correct, or the page isn't accessible offline. This causes problems for users who have installed the app to their devices.

Lighthouse flags web apps whose start URL doesn't respond with a 200 when offline:

Lighthouse audit showing start URL doesn't respond with 200 when offline

How to ensure your page is available offline

  1. If you don't already have one, add a web app manifest.
  2. Check that the start_url in your manifest is correct.
  3. Add a service worker to your app.
  4. Use the service worker to cache files locally.
  5. When offline, use the service worker as a network proxy to return the locally cached version of the file.

See the Current page does not respond with a 200 when offline guide for more information.

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