We use the adb logcat functionality a lot when developing or debugging Fennec. For example, outside of remote debugging, the quickest way to see JavaScript warnings and errors is to check the logcat, which the JS console redirects to. Sometimes, we catch a Java exception (e.g. JSONException) and log it, but we otherwise ignore the exception. Unless you are actively looking at the logcat, it's easy to miss messages like these. In other cases, we simply want a way to check the logcat when away from a computer, or when a user is not familiar with adb or remote debugging.

The LogView add-on, available now on AMO, solves some of these problems. It continuously records the logcat output and monitors it. When it sees an error in the logcat, the error is displayed as a toast for visibility.

You can also access the current logs through the new about:logs page.

The add-on only supports Jelly Bean (4.1) and above, and only Fennec logs are included rather than logs for all apps. Check out the source code or contribute on Github.

Feature suggestions are also welcome! I think the next version will have the ability to filter logs in about:logs. It will also allow you to copy logs to the clipboard and/or post logs as a pastebin link.