Adding a new locale to Nightly builds


Locales will be added to Nightly builds only after reaching at least 30% overall completion in Pontoon. For details on the requirements to move to Beta/Release, see this document.

Create a tracking GitHub issue and set up bugs to add the new locale

This GitHub project is used to track locales added to or removed from Firefox. The Queue - WIP column includes all locales currently in Nightly, once they move to Release a new column is added for the specific Firefox version in which they shipped (e.g. Firefox 91).

As a first step, file an issue using the New Locale for Firefox Desktop template. Replace %LOCALE_NAME% (%LOCALE_CODE%) with the locale name and code in the title field, e.g. Lao (lo), and add the issue to the Queue - WIP column in the GitHub project.

Then file a new tracking bug using this bug template. Replace %LOCALE_NAME% with the locale name, e.g. Lao, and %LOCALE_CODE% with the locale code, e.g. lo. Pay attention to update the alias field as well, and CC the locale manager if they already have a Bugzilla account. Once the bug is filed, update the link in the GitHub issue.

Note that the tracking bug is filed under Mozilla Localizations :: Other, as creating the Bugzilla component is a step that will be performed when the locale is ready to move to Beta/Release. If the component for this locale is already available, the bug should to be moved directly there.

To make it easier to track dependencies, also add the bug used to create the l10n-central repository (see Adding a new locale to Pontoon) as a dependency (Depends on: field) of the tracking bug.

Verify content in l10n repository

Before enabling the build, it’s a good idea to perform some basic checks:

  • Check toolkit/global/ (en-US version) for evident mistakes.

Add new locale to build configuration

First of all make sure that your environment is correctly set up, update your local mozilla-unified clone and make sure it’s on the central bookmark:

$ cd ~/mozilla/mercurial/mozilla-unified
$ hg pull -u
$ hg up central

File a bug using this template, replacing the locale name and code placeholders, and update the link in the GitHub tracking issue.

The first file to modify is browser/locales/all-locales, open it with your text editor of choice (in this example, Visual Studio Code).

$ code browser/locales/all-locales

And add the new locale to the list. With Visual Studio Code, you can open the Command Palette and select Sort Line Ascending to make sure that the list is in alphabetical order.

The second file to modify is browser/locales/l10n.toml. This is the beginning of the file:

# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at

basepath = "../.."

locales = [

Identify the locales section, and add the new locale code between double quotes, followed by a comma. As before, you can use the editor to make sure the list is in alphabetical order (make sure to select only the lines with actual locale codes before pressing running the command).

After you’ve finished editing the files, check the status of the repository, and the diff.

$ hg status
M browser/locales/all-locales
M browser/locales/l10n.toml

$ hg diff
diff --git a/browser/locales/all-locales b/browser/locales/all-locales
--- a/browser/locales/all-locales
+++ b/browser/locales/all-locales
@@ -51,17 +51,16 @@ ja

 diff --git a/browser/locales/l10n.toml b/browser/locales/l10n.toml
 --- a/browser/locales/l10n.toml
 +++ b/browser/locales/l10n.toml
 @@ -59,17 +59,16 @@ locales = [
 +    "lo",

M in hg status indicates that the file has been modified, + in hg diff that the line has been added. Follow the instructions available in this document to create a patch, submit it for review, and land it.

Verify product-details configuration

Once a locale is added to Nightly builds, product-details will pick up automatically the new build. In order for the new build to be listed on, the language name needs to be available in languages.json. If missing:

  • Open a pull request against the production branch of product-details (example), and update the GitHub tracking issue accordingly.
  • The language name needs to use Unicode code points in the format \uXXXX for non ASCII characters.

The easiest way to convert the language name from UTF-8 is to use Python's JSON module. For example, to convert Tibetan (བོད་སྐད་):

$ python -c 'import json; print(json.dumps("བོད་སྐད་"))'

The final entry in product-details would look like this (bo is the locale code for Tibetan):

"bo": {
    "English": "Tibetan",
    "native": "\u0f56\u0f7c\u0f51\u0f0b\u0f66\u0f90\u0f51\u0f0b"

Updates to product-details are pushed to production every time a new Beta or Release build is released. In case of urgency, updates can be triggered manually by Release Engineering.