If you're debugging the application update feature in Firefox or other Mozilla applications, you may need to see what requests are occurring. You can do this using the Live HTTP Headers addon to determine the URL of the update request. That URL might look something like:
You can then request this URL manually to see what's inside.
Enabling the following preferences in about:config can help troubleshoot problems with updates:
- app.update.log - for application updates;
- extensions.logging.enabled - for add-on updates.