Firefox is the web browser that was born out of the Mozilla Product Localisation project. It is now their default target and is renowned for its security.

This page contains Firefox-specific localisation notes and issues. You should read this in conjunction with the Mozilla Product Localisation pages as there are some things shared between Firefox and Thunderbird localisation.

As stated on the Mozilla Product Localisation page, there are more complete instructions about the requirements and processes involved in Mozilla localisation on the Mozilla L10n project page.


These are configurations not customisations. These are things that you must change. Remember that you need to go through a formal procedure of review to commit changes to some of these files in the Mozilla repository, especially a file like browser/chrome/browser-region/ This usually means you need to file a bug, ask for review by setting flags and more things and put people in CC. Ask at Mozilla for the newest rules.

  1. file: toolkit/
    • entry: MOZ_LANG_TITLE
    • use: Used in the language .xpi in file install.rdf. Its added to %s Language Pack
    • action: Set to the English name for your language
  2. file: browser/
    • use: Used in install.rdf’s creator tag
    • action: Set to the name of the language pack translator eg. a group, company or person
  3. file:
    • use: Credit those who helped create the language pack
    • action: you need to edit this file directly ie. not the PO file. Uncomment the MOZ_LANGPACK_CONTRIBUTORS line and make changes as needed.
  4. file: toolkit/chrome/global/
    • entry: general.useragent.locale
    • use: FIXME Assume this is the locale the browser publishes.
    • action: change to your locale xx-YY (language-COUNTRY) leave out country if you don’t need that for your language
  5. file: toolkit/chrome/global/
    • entry: intl.accept_languages
    • use: tells a website what languages you prefer your content in
    • action: set the various language settings you require
  6. file: browser/chrome/browser-region/
    • entry: general.useragent.contentlocale
    • use: unsure
    • action: change it to your country code


You can change various settings to make the browser more specific to your locale. Be aware that some changes are not allowed in official Mozilla Foundation builds.


  • Default start URL
  • Default search engine
  • Adding search engines specific to your locale
  • Bookmark customisation
  • Browser identification
  • Accepted languages

Other things to localise

This extract of an e-mail from Pavel Franc of the Czech team highlights other pieces of Firefox that need to be localised:

The Czech (cs-CZ) Thunderbird 1.0 windows builds are ready.
We do now our QA testing.

The following files outside chrome were changed in zip archive:

  * * README.txt ... translated
  * * talkback-l10n.ini ... translated
  * + cs.aff ... Czech spellchecker
  * + cs.dic ... Czech spellchecker
  * - en-US.aff ... removed
  * - en-US.dic ... removed
  * * rss.rdf ... translated
  * * mailViews.dat ... translated
  * * all-thuderbird.js ... changed useragent.locale

and in installer:
  * * install.js ... changed locale and translated shortcuts
  * * ... translated
  * * 7zSD.sfx ... translated by ResourceHacker