Provide an offline fallback page

The browser's default offline error screen ("No internet connection") is confusing and completely outside your brand. A custom offline page maintains the user experience, reinforces trust, and can surface cached content or useful actions — such as enabling users to continue reading a cached article or queuing a form submission for later.

Quick Reference

• Create a minimal /offline HTML page that works without any network requests
• Pre-cache the offline page during the service worker install event
• Intercept failed navigation requests and serve the offline page instead
• Include helpful guidance so users know what to do while offline

Check

Check whether the site shows a custom offline fallback page when the network is disconnected and a navigation request cannot be fulfilled.

Fix

Create a self-contained /offline page and configure the service worker to pre-cache it and serve it for failed navigation requests.

Explain

Explain how a service worker can intercept failed network requests and return a cached offline fallback page to the user.

Code Review

Review the service worker fetch handler and the offline page markup. Verify the offline page is pre-cached at install time, that it does not depend on external resources, and that the fallback is only served for navigation requests (not sub-resources).

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For full implementation details, code examples, and framework-specific guidance, see references/rule.md.

Rule page: https://frontendchecklist.io/en/rules/performance/offline-fallback