Service Worker Limitations and Security Considerations

Although Service Workers are powerful tools for offline capabilities, caching, background sync, and more, their usage comes with certain limitations and security requirements.

1. HTTPS Only

Service Workers can only be registered over HTTPS connections. This is implemented to protect against man-in-the-middle attacks.

• They won't work on http:// sites (except for localhost)

2. Restricted API Access

Service Workers don't have access to:

• The window object
• document and DOM manipulation
• Certain storage APIs like localStorage

They operate in a background thread within a pure JavaScript environment.

3. Limited Connection Lifetime

Service Workers aren't constantly active. They activate during specific events (fetch, push, sync) and then "sleep." For long-running operations, you should use event.waitUntil().

4. Update Management

Since Service Workers can remain in older versions on users' devices, special effort is needed to ensure timely updates, such as using skipWaiting() and clients.claim().

5. Security Best Practices

• Don't store sensitive data in cache
• Implement Content-Type validation
• Provide fallback mechanisms for error cases

Summary: Service Workers are powerful but should be used carefully and responsibly. Certain mistakes can disrupt website functionality, especially in offline mode.