The JavaScript Debugger enables you to step through JavaScript code and examine or modify its state to help track down bugs.

You can use it to debug code running locally in Firefox or running remotely, for example in a Firefox OS device or Firefox on Android. See remote debugging to learn how to connect the debugger to a remote target.

To find your way around the debugger, here's a quick tour of the UI. To find out what you can do with it, see the how-to guides below.