Firefox Mobile: Enabling the Error Console

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This page completed a technical review from Martijn Wargers (:mwargers) (Mozilla QA Team) on 2014-10-30. This article has been created from this page from QMO: Firefox Mobile: Enabling the Error Console

For Firefox 14 and greater please see the Mozilla Hacks article on Remote Debugging on Firefox for Android for web content. If you need to debug the Firefox browser itself use Android's adb logcat.

This document is obsolete the below documentation applies to Firefox 10 and lower

This tutorial assumes that you have

  • Firefox Mobile or Fennec installed on your mobile Android device

Often times it is useful and necessary to determine what is going on during the execution of a program in order to understand why something, albeit a crash, an Error or odd behaviour is happening. Viewing the Error Console is one great way to diagnose a problem, and is a perfect point of reference for developers to analyze and interpret to further acknowledge a potential or existing issue with an application or service, such as Firefox Mobile or Sync. This tutorial will provide a simple walkthrough in enabling and using the Error Console to your advantage to provide developers with necessary details to assist in investigating and solving issues apparent in the software. As the MDN DOC Center states, “The Error Console is a tool available in most Mozilla-based applications that is used for reporting errors in the application chrome and in the web pages user opens. It reports JavaScript-related errors and warnings, CSS errors and arbitrary messages from chrome code” Let us take a look at how to enable the Error Console in Firefox Mobile.

Step 1. Accessing Firefox Mobile Configuration Options

You can set user preferences via the advanced preferences editor, by typing about:config in the Location Bar. The Error Console can be enabled by searching for and toggling the preference, false to true, named: devtools.errorconsole.enabled. [caption id="attachment_25762" align="alignnone" width="210"]about:config about:config[/caption] Note: Changing any other advanced options can be harmful to the stability, security and performance of Firefox Mobile. Use with caution.

Original document information

Step 2. Accessing the Error Console

After toggling the preference from false to true, one can access the Error Console inside Firefox Mobile’s preference panes [caption id="attachment_25763" align="alignnone" width="210"]Preferences Preferences[/caption] One can access the preferences by panning to the right side of the browser and tapping the cog-wheel on the right sidebar. [caption id="attachment_25764" align="alignnone" width="150"]Error Console Error Console[/caption] From inside the preferences window, select the last available pane on the far right. This is the Error Console, and is indicated with a spider icon.

Step 3: Using the Error Console

From the Error Console one can see various types of errors that are accessible across various tabs: Error

  • Error messages occurring in JavaScript, CSS, XML, chrome, network and stack trace


  • Warnings occurring in JavaScript and CSS


  • Very similar to warnings, used very rarely

There is always information about the type of error or warning and the location of the file that was involved, and the information indicated can be useful for posting into filed bugs, whether it's a site issue or problem with the browser. Tip: Each entry can be copied to clipboard with a long hold tap on any warning, message or error and selecting 'Copy'. Additional Resources Error Console - MDC Doc Center -

  • Author(s): Aaron Train
  • Date last modified: September 6, 2012 at 2:17 pm PST