Toolbox

The Toolbox provides a single home for most of the developer tools that are built into Firefox. You can open it by selecting "Toggle Tools" from the Web Developer menu (under "Tools" on OS X and Linux, or "Firefox" on Windows), or by activating any tool hosted in it (for example, the JavaScript Debugger or the Page Inspector).

By default, the window appears docked to the bottom side of the Firefox window, but you can detach it if you like. This is what it looks like when it's docked:

The window itself is split into two parts: a toolbar along the top, and a main pane underneath:

The toolbar contains controls to activate a particular tool, to dock/float the window, and to close the window:

On the far left is a row of buttons to:

close the window
toggle the window between attached to the bottom of the browser window, and attached to the side of the browser window
toggle the window between standalone and attached to the browser window
access developer tool settings

Then there is an array of labeled buttons which enables you to switch between the different tools hosted by the Toolbox. The array may include the following tools:

Note that not all the hosted tools are always listed here: only the tools actually available in this context are shown (for example, not all tools support remote debugging yet, so if the debugging target is not the Firefox instance that launched the window, not all the hosted tools will be shown).

Next there's "Select element": this button was moved into the Toolbox toolbar from the Page Inspector in Firefox 29. If you click this button, then as you move around the web page you'll see a dotted border around each element. Click the element, and the Page Inspector will open with that element selected.

Next there's a button to activate and deactivate the split console. This enables you to use the web console without switching away from the tool you currently have active. This button's only available from Firefox 28 onwards.

Finally, the icons at the far right enable you to launch various tools whose user interfaces are not hosted by the Toolbox. From Firefox 30 the icons shown here are configurable via a setting.

Settings

Clicking the "Settings" button gives you access to settings for the Toolbox itself and for the tools it hosts:

Default Firefox Developer Tools

This group of checkboxes determines which tools are enabled in the toolbox. New tools are often included in Firefox but not enabled by default.

Available Toolbox Buttons

This setting is new in Firefox 30.

This group of checkboxes determines which "standalone tools" get buttons in the toolbar. From Firefox 31, this defaults to the node picker, the split console, and responsive design mode.

Choose DevTools theme

This enables you to switch between a light and a dark theme:

Common preferences

Settings that apply to more than one tool. There's just one of these:

Enable persistent logs: a setting to control whether or not the Web Console and Network Monitor clear their output when you navigate to a new page. Before Firefox 31, this setting only applied to the Web Console, and was listed under the Web Console.

Inspector

Default color unit: a setting to control how colors are represented in the inspected: Hex, HSL(A), RGB(A), and by name.

Web Console

Enable timestamps: controls whether the Web Console displays timestamps. From Firefox 28 the Web Console defaults to hiding timestamps.

Style Editor

These settings are available from Firefox 29 onwards

Show original sources: when a CSS preprocessor supporting source maps is used, this enables the Style Editor to display the original, preprocessor, sources rather than the generated CSS. Learn more about Style Editor support for CSS source maps. With this setting checked, the Page Inspector Rules view will also provide links to the original sources.

Autocomplete CSS: enable the Style Editor to offer autocomplete suggestions.

JavaScript Profiler

Show Gecko platform data: a setting to control whether or not profiles should include Gecko platform symbols.

Advanced settings

Disable cache: disable the browser cache to simulate first-load performance
Disable JavaScript: reload the current tab with JavaScript disabled
Enable chrome debugging: enable you to use developer tools in the context of the browser itself, and not only web content
Enable remote debugging: enable the developer tools to debug remote Firefox instances

Main Pane

The content of the main pane in the window is entirely controlled by, and specific to, the hosted tool currently selected.