https://support.mozilla.org/en-US/kb/use-firefox-interface-other-languages-language-pack

Use the Firefox interface in other languages with language packs

Language packs are add-ons that let you to have more languages available for the user interface of Firefox. This article describes how:

You always can to get Firefox available directly in your language, downloading it from www.mozilla.org/firefox/all.

If you are searching how to control the preferred languages for websites that offer its contents in multiple languages, see Settings for web content, pop-ups, fonts, and languages.

Table of Contents

How I get language packs for Firefox?

  1. Visit the Mozilla Dictionaries & Language Packs page.
  2. Find in the list the language you want to add, and click the Install Language Pack link next to it. The main page of that language pack will be open.
  3. Click the Add to Firefox button for to install it. Firefox will download the language pack and ask you to confirm the installation.
Note: If you are unable to install any language pack, see the article Unable to install add-ons (extensions or themes). If you are using a pre-release build of Firefox, you need to browse the Mozilla file servers for to find compatible language packs, even though these are only recommended for testing purposes.

How to manage language packs

To see what language packs you have installed:

  1. At the top of the Firefox window, click on the Firefox buttonOn the menu bar, click on the Tools menuAt the top of the Firefox window, click on the Tools menu, and then click Add-ons. The Add-ons Manager tab will open. Click the menu button New Fx Menu and choose Add-ons. The Add-ons Manager tab will open.

  2. In the Add-ons Manager tab, select the Languages panel.

If you don't have a Languages panel, don't worry. It's hidden if you don't have language packs installed. The same goes for a few other uncommon types of add-ons.

How to uninstall language packs

If you want to remove a language pack, see Disable or remove Add-ons.

How to change the language of the user interface

Unlike themes, enabling a language pack in the Add-ons Manager only does the languages it provides available. To change the preferred language for the interface:

  1. In the address bar, type about:config and press EnterReturn.

    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise!I accept the risk! to continue to the about:config page.
  2. In the FilterSearch field, type intl.locale.matchOS.
  3. If the intl.locale.matchOS preference has a value of true, double-click it to toggle its value to false.
  4. Clear the FilterSearch field, and type general.useragent.locale.
  5. Double-click the general.useragent.locale preference, and enter the code of the language you want to use. This page lists most of the language codes used for Mozilla localizations.

  6. At the top of the Firefox window, click on the Firefox button and then select ExitAt the top of the Firefox window, click on the File menu and then select ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select Quit.

    Click the menu button New Fx Menu and then click ExitQuit Close 29 .

When you start Firefox again, you will see the interface in the new specified language.