Internationalization for GitLab

Introduced in GitLab 9.2.

For working with internationalization (i18n), GNU gettext is used given it’s the most used tool for this task and there are a lot of applications that will help us to work with it.

Setting up GitLab Development Kit (GDK)

In order to be able to work on the GitLab Community Edition project you must download and configure it through GDK.

Once you have the GitLab project ready, you can start working on the translation.


The following tools are used:

  1. gettext_i18n_rails: this gem allow us to translate content from models, views and controllers. Also it gives us access to the following Rake tasks:
    • rake gettext:find: Parses almost all the files from the Rails application looking for content that has been marked for translation. Finally, it updates the PO files with the new content that it has found.
    • rake gettext:pack: Processes the PO files and generates the MO files that are binary and are finally used by the application.
  2. gettext_i18n_rails_js: this gem is useful to make the translations available in JavaScript. It provides the following Rake task:
    • rake gettext:po_to_json: Reads the contents from the PO files and generates JSON files containing all the available translations.
  3. PO editor: there are multiple applications that can help us to work with PO files, a good option is Poedit which is available for macOS, GNU/Linux and Windows.

Preparing a page for translation

We basically have 4 types of files:

  1. Ruby files: basically Models and Controllers.
  2. HAML files: these are the view files.
  3. ERB files: used for email templates.
  4. JavaScript files: we mostly need to work with Vue templates.

Ruby files

If there is a method or variable that works with a raw string, for instance:

def hello
  "Hello world!"


hello = "Hello world!"

You can easily mark that content for translation with:

def hello
  _("Hello world!")


hello = _("Hello world!")

Be careful when translating strings at the class or module level since these would only be evaluated once at class load time.


validates :group_id, uniqueness: { scope: [:project_id], message: _("already shared with this group") }

This would be translated when the class is loaded and result in the error message always being in the default locale.

Active Record’s :message option accepts a Proc, so we can do this instead:

validates :group_id, uniqueness: { scope: [:project_id], message: -> (object, data) { _("already shared with this group") } }
Note: Messages in the API (lib/api/ or app/graphql) do not need to be externalised.

HAML files

Given the following content in HAML:

%h1 Hello world!

You can mark that content for translation with:

%h1= _("Hello world!")

ERB files

Given the following content in ERB:

<h1>Hello world!</h1>

You can mark that content for translation with:

<h1><%= _("Hello world!") %></h1>

JavaScript files

In JavaScript we added the __() (double underscore parenthesis) function that you can import from the ~/locale file. For instance:

import { __ } from '~/locale';
const label = __('Subscribe');

In order to test JavaScript translations you have to change the GitLab localization to other language than English and you have to generate JSON files using bin/rake gettext:po_to_json or bin/rake gettext:compile.

Dynamic translations

Sometimes there are some dynamic translations that can’t be found by the parser when running bin/rake gettext:find. For these scenarios you can use the N_ method.

There is also and alternative method to translate messages from validation errors.

Working with special content


Placeholders in translated text should match the code style of the respective source file. For example use %{created_at} in Ruby but %{createdAt} in JavaScript. Make sure to avoid splitting sentences when adding links.

  • In Ruby/HAML:

     _("Hello %{name}") % { name: 'Joe' } => 'Hello Joe'
  • In Vue:

    See the section on Vue component interpolation.

  • In JavaScript (when Vue cannot be used):

     import { __, sprintf } from '~/locale';
     sprintf(__('Hello %{username}'), { username: 'Joe' }); // => 'Hello Joe'

    If you want to use markup within the translation and are using Vue, you must use the gl-sprintf component. If for some reason you cannot use Vue, use sprintf and stop it from escaping placeholder values by passing false as its third argument. You must escape any interpolated dynamic values yourself, for instance using escape from lodash.

     import { escape } from 'lodash';
     import { __, sprintf } from '~/locale';
     let someDynamicValue = '<script>alert("evil")</script>';
     // Dangerous:
     sprintf(__('This is %{value}'), { value: `<strong>${someDynamicValue}</strong>`, false);
     // => 'This is <strong><script>alert('evil')</script></strong>'
     // Incorrect:
     sprintf(__('This is %{value}'), { value: `<strong>${someDynamicValue}</strong>` });
     // => 'This is &lt;strong&gt;&lt;script&gt;alert(&#x27;evil&#x27;)&lt;/script&gt;&lt;/strong&gt;'
     // OK:
     sprintf(__('This is %{value}'), { value: `<strong>${escape(someDynamicValue)}</strong>`, false);
     // => 'This is <strong>&lt;script&gt;alert(&#x27;evil&#x27;)&lt;/script&gt;</strong>'


  • In Ruby/HAML:

     n_('Apple', 'Apples', 3)
     # => 'Apples'

    Using interpolation:

     n_("There is a mouse.", "There are %d mice.", size) % size
     # => When size == 1: 'There is a mouse.'
     # => When size == 2: 'There are 2 mice.'

    Avoid using %d or count variables in singular strings. This allows more natural translation in some languages.

  • In JavaScript:

     n__('Apple', 'Apples', 3)
     // => 'Apples'

    Using interpolation:

     n__('Last day', 'Last %d days', x)
     // => When x == 1: 'Last day'
     // => When x == 2: 'Last 2 days'

The n_ method should only be used to fetch pluralized translations of the same string, not to control the logic of showing different strings for different quantities. Some languages have different quantities of target plural forms - Chinese (simplified), for example, has only one target plural form in our translation tool. This means the translator would have to choose to translate only one of the strings and the translation would not behave as intended in the other case.

For example, prefer to use:

  n__("Project selected", "%d projects selected", selected_projects.count)

rather than:

# incorrect usage example
n_("%{project_name}", "%d projects selected", count) % { project_name: 'GitLab' }


A namespace is a way to group translations that belong together. They provide context to our translators by adding a prefix followed by the bar symbol (|). For example:

'Namespace|Translated string'

A namespace provide the following benefits:

  • It addresses ambiguity in words, for example: Promotions|Promote vs Epic|Promote
  • It allows translators to focus on translating externalized strings that belong to the same product area rather than arbitrary ones.
  • It gives a linguistic context to help the translator.

In some cases, namespaces don’t make sense, for example, for ubiquitous UI words and phrases such as “Cancel” or phrases like “Save changes” a namespace could be counterproductive.

Namespaces should be PascalCase.

  • In Ruby/HAML:


    In case the translation is not found it will return Opened.

  • In JavaScript:


Note: The namespace should be removed from the translation. See the translation guidelines for more details.

Dates / times

  • In JavaScript:
import { createDateTimeFormat } from '~/locale';

const dateFormat = createDateTimeFormat({ year: 'numeric', month: 'long', day: 'numeric' });
console.log(dateFormat.format(new Date('2063-04-05'))) // April 5, 2063

This makes use of Intl.DateTimeFormat.

  • In Ruby/HAML, we have two ways of adding format to dates and times:

    1. Through the l helper, i.e. l(active_session.created_at, format: :short). We have some predefined formats for dates and times. If you need to add a new format, because other parts of the code could benefit from it, you’ll need to add it to en.yml file.
    2. Through strftime, i.e. milestone.start_date.strftime('%b %-d'). We use strftime in case none of the formats defined on en.yml matches the date/time specifications we need, and if there is no need to add it as a new format because is very particular (i.e. it’s only used in a single view).

Best practices

Keep translations dynamic

There are cases when it makes sense to keep translations together within an array or a hash.


  • Mappings for a dropdown list
  • Error messages

To store these kinds of data, using a constant seems like the best choice, however this won’t work for translations.

Bad, avoid it:

class MyPresenter
  MY_LIST = {
    key_1: _('item 1'),
    key_2: _('item 2'),
    key_3: _('item 3')

The translation method (_) will be called when the class is loaded for the first time and translates the text to the default locale. Regardless of what’s the user’s locale, these values will not be translated again.

Similar thing happens when using class methods with memoization.

Bad, avoid it:

class MyModel
  def self.list
    @list ||= {
      key_1: _('item 1'),
      key_2: _('item 2'),
      key_3: _('item 3')

This method will memoize the translations using the locale of the user, who first “called” this method.

To avoid these problems, keep the translations dynamic.


class MyPresenter
  def self.my_list
      key_1: _('item 1'),
      key_2: _('item 2'),
      key_3: _('item 3')

Splitting sentences

Please never split a sentence as that would assume the sentence grammar and structure is the same in all languages.

For instance, the following:

{{ s__("mrWidget|Set by") }}
{{ }}
{{ s__("mrWidget|to be merged automatically when the pipeline succeeds") }}

should be externalized as follows:

{{ sprintf(s__("mrWidget|Set by %{author} to be merged automatically when the pipeline succeeds"), { author: }) }}

This also applies when using links in between translated sentences, otherwise these texts are not translatable in certain languages.

  • In Ruby/HAML, instead of:

     - zones_link = link_to(s_('ClusterIntegration|zones'), '', target: '_blank', rel: 'noopener noreferrer')
     = s_('ClusterIntegration|Learn more about %{zones_link}').html_safe % { zones_link: zones_link }

    Set the link starting and ending HTML fragments as variables like so:

     - zones_link_url = ''
     - zones_link_start = '<a href="%{url}" target="_blank" rel="noopener noreferrer">'.html_safe % { url: zones_link_url }
     = s_('ClusterIntegration|Learn more about %{zones_link_start}zones%{zones_link_end}').html_safe % { zones_link_start: zones_link_start, zones_link_end: '</a>'.html_safe }
  • In Vue, instead of:

         <gl-sprintf :message="s__('ClusterIntegration|Learn more about %{link}')">
           <template #link>

    Set the link starting and ending HTML fragments as placeholders like so:

         <gl-sprintf :message="s__('ClusterIntegration|Learn more about %{linkStart}zones%{linkEnd}')">
           <template #link="{ content }">
             >{{ content }}</gl-link>
  • In JavaScript (when Vue cannot be used), instead of:

         sprintf(s__("ClusterIntegration|Learn more about %{link}"), {
             link: '<a href="" target="_blank" rel="noopener noreferrer">zones</a>'

    Set the link starting and ending HTML fragments as placeholders like so:

         sprintf(s__("ClusterIntegration|Learn more about %{linkStart}zones%{linkEnd}"), {
             linkStart: '<a href="" target="_blank" rel="noopener noreferrer">',
             linkEnd: '</a>',

The reasoning behind this is that in some languages words change depending on context. For example in Japanese は is added to the subject of a sentence and を to the object. This is impossible to translate correctly if we extract individual words from the sentence.

When in doubt, try to follow the best practices described in this Mozilla Developer documentation.

Vue components interpolation

When translating UI text in Vue components, you might want to include child components inside the translation string. You could not use a JavaScript-only solution to render the translation, because Vue would not be aware of the child components and would render them as plain text.

For this use case, you should use the gl-sprintf component which is maintained in GitLab UI.

The gl-sprintf component accepts a message property, which is the translatable string, and it exposes a named slot for every placeholder in the string, which lets you include Vue components easily.

Assume you want to print the translatable string Pipeline %{pipelineId} triggered %{timeago} by %{author}. To replace the %{timeago} and %{author} placeholders with Vue components, here’s how you would do that with gl-sprintf:

    <gl-sprintf :message="__('Pipeline %{pipelineId} triggered %{timeago} by %{author}')">
      <template #pipelineId>{{ }}</template>
      <template #timeago>
        <timeago :time="pipeline.triggerTime" />
      <template #author>

For more information, see the gl-sprintf documentation.

Updating the PO files with the new content

Now that the new content is marked for translation, we need to update locale/gitlab.pot files with the following command:

bin/rake gettext:regenerate

This command will update locale/gitlab.pot file with the newly externalized strings and remove any strings that aren’t used anymore. You should check this file in. Once the changes are on master, they will be picked up by CrowdIn and be presented for translation.

We don’t need to check in any changes to the locale/[language]/gitlab.po files. They are updated automatically when translations from CrowdIn are merged.

If there are merge conflicts in the gitlab.pot file, you can delete the file and regenerate it using the same command.

Validating PO files

To make sure we keep our translation files up to date, there’s a linter that is running on CI as part of the static-analysis job.

To lint the adjustments in PO files locally you can run rake gettext:lint.

The linter will take the following into account:

  • Valid PO-file syntax
  • Variable usage
    • Only one unnamed (%d) variable, since the order of variables might change in different languages
    • All variables used in the message ID are used in the translation
    • There should be no variables used in a translation that aren’t in the message ID
  • Errors during translation.

The errors are grouped per file, and per message ID:

Errors in `locale/zh_HK/gitlab.po`:
  PO-syntax errors
    SimplePoParser::ParserErrorSyntax error in lines
    Syntax error in msgctxt
    Syntax error in msgid
    Syntax error in msgstr
    Syntax error in message_line
    There should be only whitespace until the end of line after the double quote character of a message text.
    Parsing result before error: '{:msgid=>["", "You are going to remove %{project_name_with_namespace}.\\n", "Removed project CANNOT be restored!\\n", "Are you ABSOLUTELY sure?"]}'
    SimplePoParser filtered backtrace: SimplePoParser::ParserError
Errors in `locale/zh_TW/gitlab.po`:
  1 pipeline
    <%d 條流水線> is using unknown variables: [%d]
    Failure translating to zh_TW with []: too few arguments

In this output the locale/zh_HK/gitlab.po has syntax errors. The locale/zh_TW/gitlab.po has variables that are used in the translation that aren’t in the message with ID 1 pipeline.

Adding a new language

Let’s suppose you want to add translations for a new language, let’s say French.

  1. The first step is to register the new language in lib/gitlab/i18n.rb:

      'fr' => 'Français'
  2. Next, you need to add the language:

    bin/rake gettext:add_language[fr]

    If you want to add a new language for a specific region, the command is similar, you just need to separate the region with an underscore (_). For example:

    bin/rake gettext:add_language[en_GB]

    Please note that you need to specify the region part in capitals.

  3. Now that the language is added, a new directory has been created under the path: locale/fr/. You can now start using your PO editor to edit the PO file located in: locale/fr/gitlab.edit.po.

  4. After you’re done updating the translations, you need to process the PO files in order to generate the binary MO files and finally update the JSON files containing the translations:

    bin/rake gettext:compile
  5. In order to see the translated content we need to change our preferred language which can be found under the user’s Settings (/profile).

  6. After checking that the changes are ok, you can proceed to commit the new files. For example:

    git add locale/fr/ app/assets/javascripts/locale/fr/
    git commit -m "Add French translations for Value Stream Analytics page"