---
title: The Firefox JavaScript Debugger
slug: Tools/Debugger
tags:
  - Debugger
  - Debugging
  - Dev Tools
  - JavaScript
  - NeedsTranslation
  - Tools
  - TopicStub
  - 'l10n:priority'
translation_of: Tools/Debugger
---
<div>{{ToolsSidebar}}</div>

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

<p>{{EmbedYouTube("QK4hKWmJVLo")}}</p>

<p>You can use it to debug code running locally in Firefox or running remotely, for example on an Android device running Firefox for Android. See <a href="/en-US/docs/Tools/Remote_Debugging">remote debugging </a>to learn how to connect the debugger to a remote target.</p>

<p>To find your way around the debugger, here's a <a href="/en-US/docs/Tools/Debugger/UI_Tour">quick tour of the UI</a>.</p>

<h2 id="How_to">How to</h2>

<p>To find out what you can do with the debugger, see the following how-to guides:</p>

<div class="twocolumns">
<ul>
 <li><a href="/en-US/docs/Tools/Debugger/How_to/Open_the_debugger">Open the debugger</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/How_to/Set_a_breakpoint">Set a breakpoint</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/How_to/Set_a_conditional_breakpoint">Set a conditional breakpoint</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/Set_an_XHR_breakpoint">Set an XHR breakpoint</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/Set_a_logpoint">Set a logpoint</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/Set_event_listener_breakpoints">Set event listener breakpoints</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/How_to/Disable_breakpoints">Disable breakpoints</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/How_to/Step_through_code">Step through code</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/How_to/Breaking_on_exceptions">Break on exceptions</a></li>
 <li><a href="https://developer.mozilla.org/en-US/docs/Tools/Debugger/How_to/Set_Watch_Expressions">Set watch expressions</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/Debug_worker_threads">Debug worker threads</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/How_to/Pretty-print_a_minified_file">Pretty-print a minified file</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/How_to/Search">Search</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/How_to/Debug_eval_sources">Debug eval sources</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/How_to/Use_a_source_map">Use a source map</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/How_to/Use_watchpoints">Use watchpoints</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/Break_on_DOM_mutation">Break on DOM Mutation</a></li>
</ul>
</div>

<hr>
<h2 id="Reference">Reference</h2>

<div class="twocolumns">
<ul>
 <li><a href="/en-US/docs/Tools/Debugger/Keyboard_shortcuts">Keyboard shortcuts</a></li>
 <li><a href="/en-US/docs/Tools/Debugger/Source_map_errors">Source map errors</a></li>
</ul>
</div>