Chrome and Root folders

There are 2 relevant folders that we modify to patch Firefox:

The chrome folder

The fastest way to find it is to just type about:support on the URL bar of your firefox, and then click the open folder button inside the profile folder section. After this, your profile folder will be open.

You may or may not see the chrome folder. If you don't see it, just create it and place inside the userContent.css and userChrome.css files.

If you want to know the exact location for profile folders:

On Windows 7 and above, profile folders are in this location, by default:

C:\Users\(Your username)\AppData\Roaming\Mozilla\Firefox\Profiles\(profile folder)

If you have never used userChrome.css or userContent.css before, you will have to create a folder named "chrome" inside the profile folder, which is where you will have to place these files.

This is where you would have to place the files once you have created the chrome folder:

C:\Users\(Your username)\AppData\Roaming\Mozilla\Firefox\Profiles\(profile folder)\chrome\

The AppData folder is a hidden folder; to show hidden folders, open a Windows Explorer window and choose "Tools → Folder Options → View (tab) → Show hidden files and folders".

You can also use this path to find the profile folder, even when it is hidden:

%APPDATA%\Mozilla\Firefox\Profiles\(profile folder)

On Firefox portable, the profile folder location depends on where you placed the portable folder

For example, if you placed your portable firefox directly on C:\FirefoxPortable, your profile folder will be in here:

C:\FirefoxPortable\Data\Profile

...and the chrome folder here:

C:\FirefoxPortable\Data\Profile\chrome\

On Linux, profile folders are located in this other location:

/home/(Your-username)/.mozilla/firefox/(profile folder)

If you have never used userChrome.css or userContent.css before, you will have to create a folder named "chrome" inside the profile folder, which is where you will have to place these files.

This is where you would have to place the files once you have created the chrome folder:

/home/(Your-username)/.mozilla/firefox/(profile folder)/chrome/

The ".mozilla" folder is a hidden folder. To show hidden files in Nautilus (Gnome desktop's default file browser), choose "View -> Show Hidden Files". On others such as Dolphin (Kubuntu's default file browser), you'd have to choose "Control -> Hidden files"

On Mac, profile folders are in one of these locations:

~/Library/Application Support/Firefox/Profiles/(profile folder)
~/Library/Mozilla/Firefox/Profiles/(profile folder)

If you have never used userChrome.css or userContent.css before, you will have to create a folder named "chrome" inside the profile folder, which is where you will have to place these files.

This is where you would have to place the files once you have created the chrome folder:

~/Library/Application Support/Firefox/Profiles/(profile folder)/chrome
~/Library/Mozilla/Firefox/Profiles/(profile folder)/chrome/

The tilde character (~) refers to the current user's Home folder, so ~/Library is the /Macintosh HD/Users/(username)/Library folder. For OS X 10.7 Lion and above, the ~/Library folder is hidden by default.

You can make them visible by either pressing a combination of keys:

CMD + SHIFT + .

... or issuing this command in the terminal:

defaults write com.apple.finder AppleShowAllFiles TRUE
killall Finder

This will also cause any file icons to take on a hazy, 50% alpha look. To restore the old settings (hide the files and make the icons look normal) press the same keys combination, or issue the commands again, but entering FALSE instead of TRUE.

Firefox root folder

The root folder is where both the executable and the "defaults" folder of your current installed firefox are located

For Windows, you can find firefox root folder here:

32bits Firefox -> C:\Program Files (x86)\Mozilla Firefox\
64bits Firefox -> C:\Program Files\Mozilla Firefox\

If you have a 32-bits Windows, you will only see the 64-bits path.

On Firefox portable, the root folder location depends on where you placed the portable folder.

Following the previous example of the profile directory for firefox portable, if you placed your portable firefox on C:\FirefoxPortable, the root folder will be in one of these:

C:\FirefoxPortable\App\Firefox
C:\FirefoxPortable\App\Firefox64

Where the Firefox64 corresponds to a 64-bits system (most modern computers will use this one), and the Firefox without number will correspond to the 32-bits one.

For Linux, you can find the root folder by default in this path:

/usr/lib/firefox/browser

In some cases you might find a difference between 32 and 64 bits program installation paths in Linux, in that case you'd find the path here:

/usr/lib64/firefox/browser

The installation directory path may also vary depending on the distribution, and if you use a package manager to install the application from their repository.

For Mac, you can find the root folder in this path:

/Applications/Firefox.app/Contents/resources

To open "Firefox.app", Ctrl-click it and select Show Package Contents. If you simply click it, you will start the application.