Command line options

Command line options are used to specify various startup options for Mozilla applications. For example, if you have multiple profiles you can use command line configuration options to bypass the Profile Manager and open a specific profile. You can also control how Mozilla applications open, which components open initially, and what the components do when they open. This page describes the commonly used options and how to use them. You can open the command line interface by pressing shift + F2.

Syntax rules

But first, let's describe the syntax rules that apply for all options.

  • Command parameters containing spaces must be enclosed in quotes, such as "Joel User".
  • Command actions are case insensitive.
  • Command parameters, except profile names, are case insensitive.
  • Blank spaces ( ) separate commands and parameters.
  • Each message option follows the syntax field=value, for example:
    • subject=cool page
    • attachment='file:///c:/test.txt'
    • body=check this page or also in Thunderbird 52 and newer: body=c:\path\to\file.txt
  • Separate multiple message options by comma (,), for example: ",subject=cool page" . Comma separators must not follow or precede spaces ( ).
  • To assign multiple values to a field, enclose the values in single quotes ('), for example: "to=',',subject=cool page" .

Using command line options

Command line options follow the command to start the application. If the option contains arguments, enter the argument after the option. Some options have abbreviations, for example, "-editor" can be abbreviated as "-edit" (available abbreviations are described in the text below). In some cases, option arguments must be enclosed in quotation marks (this is noted in the option descriptions below). Multiple command line options can be specified. In general, the syntax is as follows:

application -option -option "argument" -option argument


The following examples show the use of the "-ProfileManager" command, which will open the profile manager prior to starting Firefox or Thunderbird:


Select run from Windows start menu. Enter the following command:

firefox -ProfileManager

Mac OS X

Go to applications > utilities. Open terminal and enter the following command:

cd /Applications/
./firefox -ProfileManager

If you use Firefox Nightly, you can enter:

cd /Applications/
./firefox -ProfileManager


Open terminal and enter the following command:

cd Thunderbird installation directory
./thunderbird -ProfileManager

The example above invokes the "-ProfileManager" command line option with Mozilla's Thunderbird mail client.

User profile


Firefox 67's downgrade protection prevents accidentally starting Firefox in a profile running a later version of Firefox. Depending on changes between the two versions, some files in a profile may not be downwards compatible. Adding this option bypasses downgrade protection.

-CreateProfile profile_name

Create a new profile in the default directory, but do not start the application. The profile will be named profile_name in the profile manager, the profile_name must not contain spaces ( ). Do not run profile_name while running an instance of the application, you can use the -no-remote option to avoid connecting to a running instance.

firefox -CreateProfile JoelUser

-CreateProfile "profile_name profile_dir"

Creates a new profile in the profile_dir directory, but do not start the application. The profile will be named profile_name in the profile manager. Note profile_name and profile_dir are quoted together, and are separated by exactly 1 space (as with the previous syntax, profile_name must not contain spaces).

Do not run profile_dir while running an instance of the application. You can use the -no-remote option to avoid connecting to a running instance.

firefox -CreateProfile "JoelUser c:\internet\joelusers-moz-profile"

Note: profile_dir must not exist and you must not already have a profile called profile_name.


Start with import wizard.


Open new instance, not a new window in running instance, which allows multiple copies of application to be open at a time.

firefox -new-instance -P "Another Profile"

Note: Not available for Windows, see bug 855899.


Do not accept or send remote commands. Implies -new-instance.

firefox -no-remote -P "Another Profile"

Note: Since Firefox 9, this does really mean what its name implies on all platforms, i.e. instances created with this parameter do not accept or send remote commands, see bug 650078. That means that such instances won't be re-used. Also when using this argument a new instance is created in any case.

-override /path/to/override.ini

Load the specified override.ini file to override application.ini (browser/app/application.ini). This can be used to suppress the migration wizard at startup by loading the following override.ini. Firefox only.



Start with profile manager. Short form: -P without a profile name.

-P "profile_name"

Bypass profile manager and launch application with the profile named profile_name. Useful for dealing with multiple profiles.

firefox -P "Joel User"

Note: profile_name is case sensitive. If you don't specify a profile name then the profile manager is opened instead.
You must use an upper case P on Linux with versions older than 7.x, as there lower case invokes purify mode (memory and leak detection). Other platforms accept both upper and lower case.

-profile "profile_path"

Start with the profile with the given path. Firefox, Thunderbird and SeaMonkey2.x only.

"profile_path" can either be an absolute path ("/path/to/profile") or a relative path ("path/to/profile").

Note: On Mac OS X specifying a relative path is not supported anymore from Firefox 4.0 and up due to a regression, see bug 673955.



Start with the browser component. Firefox and SeaMonkey only.


Make this instance the active application.

-new-tab URL

Open URL in a new tab. Firefox and SeaMonkey2.x only.

-new-window URL

Open URL in a new window. Firefox and SeaMonkey2.x only.

--kiosk URL

Open URL full screen without user interface. Firefox 71 and later.


Open options/preferences window. Firefox and SeaMonkey2.x only.


Opens Firefox in permanent private browsing mode. Firefox 3.6 and later only.

May not be applicable in older Ubuntu for Firefox 20 and later, confirmed to work in 14.04.


Opens a new private browsing window in an existing instance of Firefox. Firefox 20 and later only.

-private-window URL

Open URL in a new private browsing window. If a private browsing window is already open, a new tab is opened in the existing window. Firefox 29 and later only. Does not work in Firefox 31 on linux mint 17 nor on Firefox 48 on Windows 7. URL opens in a non-private window.

-search term

Search term with your default search engine. Firefox and SeaMonkey 2.1 and later only.


Set the application as the default browser. Firefox only.

-url URL

Open URL in a new tab or window, depend on the browser option. -url can be omitted. You may list multiple URLs, separated by spaces. Firefox and SeaMonkey only.


Note: When opening multiple URLs, Firefox always opens them as tabs in a new window.



Start with address book. Thunderbird and SeaMonkey only.

-compose message_options

Start with mail composer. See syntax rules. Thunderbird and SeaMonkey only.

thunderbird -compose ""


Start with the mail client. Thunderbird and SeaMonkey only.

-news news_URL

Start with the news client. If news_URL (optional) is given, open the specified newsgroup. Thunderbird and SeaMonkey only.

thunderbird -news news://server/group


Open options/preferences window. Thunderbird only.


Start with the offline mode. Thunderbird and SeaMonkey only.


Set the application as the default email client. Thunderbird only.



Start with the calendar client. Sunbird only.

-showdate date

Show your schedule of the given date. Sunbird only.

sunbird -showdate 08/04/2008

-subscribe URL or -url URL

Subscribe to the given URL. Sunbird only.

Other components


Start with the IRC client, ChatZilla, if installed.


Start with native developer tools opened.

-editor URL or -edit URL

Start with editor (composer) for the given URL (where URL is optional). SeaMonkey only.

seamonkey -edit

-inspector URL

Start with the DOM Inspector, if installed, and inspect the given URL (where URL is optional).


Start application with browser toolbox (formerly browser debugger). That is different to Venkman debugger (see option -venkman).


Start application with the error console, or, in Firefox, the browser console.


Gecko (layout engine) has a JavaScript cache, which is not reset on startup, this clears it.

-start-debugger-server port

Firefox only. Start the debugger server on port. This will enable another instance of Firefox to connect the Firefox developer tools to this Firefox instance. See the article on remotely debugging Firefox desktop.

The port argument is optional, and if it is omitted, the server will listen on port 6000.


Start with the JavaScript debugger, Venkman, if installed.


-app /path/to/application.ini

Start a new process running the XULRunner application at path/to. Also works with Firefox version 3 and above.

--install-app path/to/myapplication.(xpi|xulapp)

Installs the XULRunner application at path/to onto the system. Applications are installed into the default location for your system (e.g., Program Files, Applications, usr, lib) at vendorname/applicationName. Applications may be uninstalled per usual methods for your system.

"C:\Program Files\Mozilla XULRunner\\xulrunner\xulrunner.exe" --install-app "C:\Users\Billdo\Desktop\myapplication.xpi"
/opt/xulrunner/ --install-app ~/Desktop/myapplication.xulapp
/Library/Frameworks/XUL.framework/xulrunner-bin --install-app ~/Desktop/myapplication.xpi


Registers XULRunner on the system for all users. Must be run as admin / root.


Registers XULRunner for a single user.


Unregisters XULRunner for all users.


Unregisters XULRunner for a single user.


-chrome chrome_URL

Load the specified chrome.

firefox -chrome chrome://inspector/content

-register chrome_URL

Register the specified chrome, but do not start application.


Gecko 1.9.2 note
-install-global-extension and -install-global-theme have been removed from Gecko 1.9.2 and upwards.

-install-global-extension /path/to/extension

Installs the extension into the application directory. The parameter is the path to the extension. You must have administrative privileges.

-install-global-theme /path/to/theme

Same as above, but for themes. You must have administrative privileges.

Note: Since Firefox, use of the -install-global-extension and -install-global-theme command line arguments have been restricted to only allow installing add-ons that are on local disks or mapped drives. Installing from a network share directly will no longer succeed.


Launches the application with all extensions disabled, for that launch only (extensions are not loaded, but are not permanently disabled in the extension manager data source).

Remote control

-remote remote_command

This feature was removed in Firefox 36.0, restored in 36.0.1 and removed again in 39.0. See bug 1080319.

Execute the specified remote_command in an already running application process.

firefox -remote "openURL(, new-tab)"

This option is only available on X-Windows Unix platforms.



Write messages for the debugging console into the window which launched the application instead of opening a new window for the debugging messages. Only supported on the Windows operating system.


Start application with a debugging console.

Note: Windows only.

-h or -help or -?

Print the list of all available command line options. Note that on Windows this only works with a redirection such as |more (bug 355889). This option is available only in a command console.


Tells the application that it is being launched by the OS shell. This should not be specified unless the caller provides all of the functionality provided by the OS shell when launching the application (bug 384384).


Tells the application that there will be a Windows DDE request to open the same url specified on the command line. This should not be specified unless the caller provides all of the functionality provided by the OS shell when launching the application (bug 354005).


Don't open default windows. Useful with those command-line arguments that open their own windows but don't already prevent default windows from opening. Firefox, Thunderbird3.x and SeaMonkey2.x only.

-v or -version

Print application version. Note that on Windows this only works with a redirection such as |more (bug 355889). This option is available only in a command console.

X11 options

These options are only available for an application build for and running atop the X11/ display and window system to be found on Linux and other Unix-based systems.


Set the WM_CLASS resource class of the X11 windows created by the application.


Set the X display to use.


Make all warnings fatal.


Make X calls synchronous.

Other options need to be documented


Original Document Information

  • Author(s): Ben Goodger, Steffen Wilberg, Seth Spitzer, Daniel Wang
  • Copyright Information: Portions of this content are © 1998–2007 by individual contributors; content available under a Creative Commons license | Details.