From MozillaZine Knowledge Base
The installation directory is the directory where a Mozilla application stores its program files. It is usually a directory on your own computer. This applies to all Mozilla applications, including Firefox, Thunderbird, Mozilla Suite and SeaMonkey.
The installation directory is also known by the terms "program directory", "application directory", "program folder", and similar phrases.
Important: The installation directory does not include your preference settings or user data such as passwords, cookies, bookmarks or address books. That information is normally stored in the profile folder for your Mozilla application, in a separate location.
Finding the installation directory
If you can start a Mozilla application by using a shortcut or launcher icon, then you can usually see where its installation directory is located by context-clicking (right-clicking) the icon and looking at the properties.
The following sections give examples of the default installation directory for various operating systems and applications. The actual directory on your system might not be the default if you chose a different installation directory when you installed the application.
If you cannot find the installation directory in either of these ways, then you can try searching your computer's file system. The following sections also give examples of names to search for.
Examples of default installation directories:
Example search for Firefox: firefox.exe
Examples of default installation directories (32-bit Linux):
Examples of default installation directories (64-bit Linux):
The installation directory path may vary depending on the distribution if you use a package manager to install the application from their repository.
Example search for Firefox (searching from / ): firefox
Mac OS X
Examples of default installation directories (folders):
To open one of these folders, Ctrl-click it and select Show Package Contents. If you simply click it, you will start the application.
Example search for Firefox: Firefox.app