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:
  • to=foo@nowhere.net
  • subject=cool page
  • attachment=www.mozilla.org
  • 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: "to=foo@nowhere.net,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='foo@nowhere.net,foo@foo.de',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

Examples

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

Windows

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

firefox -ProfileManager

macOS

Go to Applications ▶︎ Utilities. Open terminal and enter the following command:

cd /Applications/Firefox.app/Contents/MacOS
./firefox -ProfileManager

If you use Firefox Nightly, you can enter:

cd /Applications/FirefoxNightly.app/Contents/MacOS
./firefox -ProfileManager

Linux

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

-allow-downgrade

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"

-migration

Start with import wizard.

-new-instance

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"

-no-remote

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

firefox -no-remote -P "Another Profile"

-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.

[XRE]
EnableProfileMigrator=0

-ProfileManager

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"

-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").

Browser

-browser

Start with the browser component. Firefox and SeaMonkey only.

-foreground

Make this instance the active application.

-headless

Runs Firefox in headless mode, which is very useful for purposes such as debugging and automated testing. Available in Firefox 55+ on Linux, and Firefox 56+ on Windows/Mac OS X.

-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.

-preferences

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

-private

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.

-private-window

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.

-setDefaultBrowser

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.

firefox www.mozilla.com
firefox www.mozilla.com developer.mozilla.org

Mail/news

-addressbook

Start with address book. Thunderbird and SeaMonkey only.

-compose message_options

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

thunderbird -compose "to=foo@nowhere.net"

-mail

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

-options

Open options/preferences window. Thunderbird only.

-offline

Start with the offline mode. Thunderbird and SeaMonkey only.

-setDefaultMail

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

Calendar

-calendar

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

-chat

Start with the IRC client, ChatZilla, if installed.

-devtools

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 www.mozilla.org

-inspector URL

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

-jsdebugger

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

-jsconsole

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

-purgecaches

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.

-venkman

Start with the JavaScript debugger, Venkman, if installed.

XULRunner

-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\1.8.0.4\xulrunner\xulrunner.exe" --install-app "C:\Users\Billdo\Desktop\myapplication.xpi"

/opt/xulrunner/1.8.0.4/xulrunner/xulrunner --install-app ~/Desktop/myapplication.xulapp

/Library/Frameworks/XUL.framework/xulrunner-bin --install-app ~/Desktop/myapplication.xpi

--register-global

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

--register-user

Registers XULRunner for a single user.

--unregister-global

Unregisters XULRunner for all users.

--unregister-user

Unregisters XULRunner for a single user.

Chrome

-chrome chrome_URL

Load the specified chrome.

firefox -chrome chrome://inspector/content

-register chrome_URL

Register the specified chrome, but do not start application.

Add-ons

-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.

-safe-mode

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

Execute the specified remote_command in an already running application process.

firefox -remote "openURL(www.mozilla.org, new-tab)"

Miscellaneous

-attach-console

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.

-console

Start application with a debugging console.

-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.

-osint

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).

-requestPending

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).

-silent

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/X.org display and window system to be found on Linux and other Unix-based systems.

--class=WM_CLASS

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

--display=DISPLAY

Set the X display to use.

--g-fatal-warnings

Make all warnings fatal.

--sync

Make X calls synchronous.

Other options need to be documented

• -print-xpcom-dir
• -print-xpcom-dirlist
• -kill
• -killAll
• -f
• -ftimeout
• -fwait
• -unsetDefaultMail
• GTK options
• -no-deelevate (Running Windows as Administrator with Launcher Process Enabled Causes Drag and Drop Errors - How to Fix)

References

• Chrome: Command Line
• Test Documentation for Command-line Features (mozilla.org)
• toolkit/xre/nsAppRunner.cpp
• browser/components/nsBrowserContentHandler.js
• suite/browser/nsBrowserContentHandler.js
• mail/components/nsMailDefaultHandler.js
• Installer command line options