wagtail/docs/advanced_topics/i18n.rst

====================
Internationalisation
====================

.. contents::
    :local:
    :depth: 3

.. _multi_language_content:

Multi-language content
======================

.. versionadded:: 2.11

Overview
--------

Out of the box, Wagtail assumes all content will be authored in a single language.
This document describes how to configure Wagtail for authoring content in
multiple languages.

.. note::
    Wagtail provides the infrastructure for creating and serving content in multiple languages,
    but does not itself provide an admin interface for managing translations of the same content
    across different languages. For this, the `wagtail-localize <https://github.com/wagtail/wagtail-localize>`_
    app must be installed separately.

This document only covers the internationalisation of content managed by Wagtail.
For information on how to translate static content in template files, JavaScript
code, etc, refer to the `Django internationalisation docs <https://docs.djangoproject.com/en/3.1/topics/i18n/translation/>`_.
Or, if you are building a headless site, refer to the docs of the frontend framework you are using.

Wagtail's approach to multi-lingual content
-------------------------------------------

This section provides an explanation of Wagtail's internationalisation approach.
If you're in a hurry, you can skip to `Configuration`_.

In summary:

 - Wagtail stores content in a separate page tree for each locale
 - It has a built-in ``Locale`` model and all pages are linked to a ``Locale`` with the ``locale`` foreign key field
 - It records which pages are translations of each other using a shared UUID stored in the ``translation_key`` field
 - It automatically routes requests through translations of the site's homepage
 - It uses Django's ``i18n_patterns`` and ``LocaleMiddleware`` for language detection

Page structure
^^^^^^^^^^^^^^

Wagtail stores content in a separate page tree for each locale.

For example, if you have two sites in two locales, then you will see four
homepages at the top level of the page hierarchy in the explorer.

This approach has some advantages for the editor experience as well:

 - There is no default language for editing, so content can be authored in any
   language and then translated to any other.
 - Translations of a page are separate pages so they can be published at
   different times.
 - Editors can be given permission to edit content in one locale and not others.

How locales and translations are recorded in the database
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

All pages (and any snippets that have translation enabled) have a ``locale`` and
``translation_key`` field:

 - ``locale`` is a foreign key to the ``Locale`` model
 - ``translation_key`` is a UUID that's used to find translations of a piece of content.
   Translations of the same page/snippet share the same value in this field

These two fields have a 'unique together' constraint so you can't have more than
one translation in the same locale.

Translated homepages
^^^^^^^^^^^^^^^^^^^^

When you set up a site in Wagtail, you select the site's homepage in the 'root page'
field and all requests to that site's root URL will be routed to that page.

Multi-lingual sites have a separate homepage for each locale that exist as siblings
in the page tree. Wagtail finds the other homepages by looking for translations of
the site's 'root page'.

This means that to make a site available in another locale, you just need to
translate and publish its homepage in that new locale.

If Wagtail can't find a homepage that matches the user's language, it will fall back
to the page that is selected as the 'root page' on the site record, so you can use
this field to specify the default language of your site.

Language detection and routing
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

For detecting the user's language and adding a prefix to the URLs
(``/en/``, ``/fr-fr/``, for example), Wagtail is designed to work with Django's
builtin internationalisation utilities such as ``i18n_patterns`` and
`LocaleMiddleware`. This means that Wagtail should work seamlessly with any
other internationalised Django applications on your site.

Locales
~~~~~~~

The locales that are enabled on a site are recorded in the ``Locale`` model in
``wagtailcore``. This model has just two fields: ID and ``language_code`` which
stores the `BCP-47 language tag <https://en.wikipedia.org/wiki/IETF_language_tag>`_
that represents this locale.

The locale records can be set up with an :ref:`optional management UI <enabling_locale_management>` or created
in the shell. The possible values of the ``language_code`` field are controlled
by the ``WAGTAIL_CONTENT_LANGUAGES`` setting.

 .. note:: Read this if you've changed ``LANGUAGE_CODE`` before enabling internationalisation

    On initial migration, Wagtail creates a ``Locale`` record for the language that
    was set in the ``LANGUAGE_CODE`` setting at the time the migration was run. All
    pages will be assigned to this ``Locale`` when Wagtail's internationalisation is disabled.

    If you have changed the ``LANGUAGE_CODE`` setting since updating to Wagtail 2.11,
    you will need to manually update the record in the ``Locale`` model too before
    enabling internationalisation, as your existing content will be assigned to the old code.

Configuration
-------------

In this section, we will go through the minimum configuration required to enable
content to be authored in multiple languages.

.. contents::
    :local:
    :depth: 1

.. _enabling_internationalisation:

Enabling internationalisation
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

To enable internationalisation in both Django and Wagtail, set the following
settings to ``True``:

.. code-block:: python

    # my_project/settings.py

    USE_I18N = True
    WAGTAIL_I18N_ENABLED = True

In addition, you might also want to enable Django's localisation support. This
will make dates and numbers display in the user's local format:

.. code-block:: python

    # my_project/settings.py

    USE_L10N = True

Configuring available languages
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Next we need to configure the available languages. There are two settings
for this that are each used for different purposes:

 - ``LANGUAGES`` - This sets which languages are available on the frontend of the site.
 - ``WAGTAIL_CONTENT_LANGUAGES`` - This sets which the languages Wagtail content
   can be authored in.

You can set both of these settings to the exact same value. For example, to
enable English, French, and Spanish:

.. code-block:: python

    # my_project/settings.py

    WAGTAIL_CONTENT_LANGUAGES = LANGUAGES = [
        ('en', "English"),
        ('fr', "French"),
        ('es', "Spanish"),
    ]

.. note::

    Whenever ``WAGTAIL_CONTENT_LANGUAGES`` is changed, the ``Locale`` model needs
    to be updated as well to match.

    This can either be done with a data migration or with the optional locale
    management UI described in the next section.

You can also set these to different values. You might want to do this if you
want to have some programmatic localisation (like date formatting or currency,
for example) but use the same Wagtail content in multiple regions:

.. code-block:: python

    # my_project/settings.py

    LANGUAGES = [
        ('en-GB', "English (Great Britain)"),
        ('en-US', "English (United States)"),
        ('en-CA', "English (Canada)"),
        ('fr-FR', "French (France)"),
        ('fr-CA', "French (Canada)"),
    ]

    WAGTAIL_CONTENT_LANGUAGES = [
        ('en-GB', "English"),
        ('fr-FR', "French"),
    ]

When configured like this, the site will be available in all the different
locales in the first list, but there will only be two language trees in
Wagtail.

All the ``en-`` locales will use the "English" language tree, and the ``fr-``
locales will use the "French" language tree. The differences between each locale
in a language would be programmatic. For example: which date/number format to
use, and what currency to display prices in.

.. _enabling_locale_management:

Enabling the locale management UI (optional)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

An optional locale management app exists to allow a Wagtail administrator to
set up the locales from the Wagtail admin interface.

To enable it, add ``wagtail.locales`` into ``INSTALLED_APPS``:

.. code-block:: python

    # my_project/settings.py

    INSTALLED_APPS = [
        # ...
        'wagtail.locales',
        # ...
    ]

Adding a language prefix to URLs
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

To allow all of the page trees to be served at the same domain, we need
to add a URL prefix for each language.

To implement this, we can use Django's built-in
`i18n_patterns <https://docs.djangoproject.com/en/3.1/topics/i18n/translation/#language-prefix-in-url-patterns>`_
function, which adds a language prefix to all of the URL patterns passed into it.
This activates the language code specified in the URL and Wagtail takes this into
account when it decides how to route the request.

In your project's ``urls.py`` add Wagtail's core URLs (and any other URLs you
want to be translated) into an ``i18n_patterns`` block:

.. code-block:: python

    # /my_project/urls.py

    ...

    from django.conf.urls.i18n import i18n_patterns

    # Non-translatable URLs
    # Note: if you are using the Wagtail API or sitemaps,
    # these should not be added to `i18n_patterns` either
    urlpatterns = [
        path('django-admin/', admin.site.urls),

        path('admin/', include(wagtailadmin_urls)),
        path('documents/', include(wagtaildocs_urls)),
    ]

    # Translatable URLs
    # These will be available under a language code prefix. For example /en/search/
    urlpatterns += i18n_patterns(
        path('search/', search_views.search, name='search'),
        path("", include(wagtail_urls)),
    )

User language auto-detection
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

After wrapping your URL patterns with ``i18n_patterns``, your site will now
respond on URL prefixes. But now it won't respond on the root path.

To fix this, we need to detect the user's browser language and redirect them
to the best language prefix. The recommended approach to do this is with
Django's ``LocaleMiddleware``:

.. code-block:: python

    # my_project/settings.py

    MIDDLEWARE = [
        # ...
        'django.middleware.locale.LocaleMiddleware',
        # ...
    ]

Custom routing/language detection
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

You don't strictly have to use ``i18n_patterns`` or ``LocaleMiddleware`` for
this and you can write your own logic if you need to.

All Wagtail needs is the language to be activated (using Django's
``django.utils.translation.activate`` function) before the
``wagtail.core.views.serve`` view is called.

Recipes for internationalised sites
-----------------------------------

Language/region selector
^^^^^^^^^^^^^^^^^^^^^^^^

Perhaps the most important bit of internationalisation-related UI you can add
to your site is a selector to allow users to switch between different
languages.

If you're not convinced that you need this, have a look at https://www.w3.org/International/questions/qa-site-conneg#yyyshortcomings for some rationale.

Basic example
~~~~~~~~~~~~~

Here is a basic example of how to add links between translations of a page.

This example, however, will only include languages defined in
``WAGTAIL_CONTENT_LANGUAGES`` and not any extra languages that might be defined
in ``LANGUAGES``. For more information on what both of these settings mean, see
`Configuring available languages`_.

If both settings are set to the same value, this example should work well for you,
otherwise skip to the next section that has a more complicated example which takes
this into account.

.. code-block:: html+Django

    {# make sure these are at the top of the file #}
    {% load i18n wagtailcore_tags %}

    {% if page %}
        {% for translation in page.get_translations.live %}
            {% get_language_info for translation.locale.language_code as lang %}
            <a href="{% pageurl translation %}" rel="alternate" hreflang="{{ language_code }}">
                {{ lang.name_local }}
            </a>
        {% endfor %}
    {% endif %}

Let's break this down:

.. code-block:: html+Django

    {% if page %}
        ...
    {% endif %}

If this is part of a shared base template it may be used in situations where no page object is available, such as 404 error responses, so check that we have a page before proceeding.

.. code-block:: html+Django

    {% for translation in page.get_translations.live %}
        ...
    {% endfor %}

This ``for`` block iterates through all published translations of the current page.

.. code-block:: html+Django

    {% get_language_info for translation.locale.language_code as lang %}

This is a Django built-in tag that gets info about the language of the translation.
For more information, see `get_language_info() in the Django docs <https://docs.djangoproject.com/en/3.1/topics/i18n/translation/#django.utils.translation.get_language_info>`_.

.. code-block:: html+Django

    <a href="{% pageurl translation %}" rel="alternate" hreflang="{{ language_code }}">
        {{ lang.name_local }}
    </a>

This adds a link to the translation. We use ``{{ lang.name_local }}`` to display
the name of the locale in its own language. We also add ``rel`` and ``hreflang``
attributes to the ``<a>`` tag for SEO.

Handling locales that share content
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Rather than iterating over pages, this example iterates over all of the configured
languages and finds the page for each one. This works better than the `Basic example`_
above on sites that have extra Django ``LANGUAGES`` that share the same Wagtail content.

For this example to work, you firstly need to add Django's
`django.template.context_processors.i18n <https://docs.djangoproject.com/en/3.1/ref/templates/api/#django-template-context-processors-i18n>`_
context processor to your ``TEMPLATES`` setting:

.. code-block:: python

    # myproject/settings.py

    TEMPLATES = [
        {
            # ...
            'OPTIONS': {
                'context_processors': [
                    # ...
                    'django.template.context_processors.i18n',
                ],
            },
        },
    ]

Now for the example itself:

.. code-block:: html+Django

    {% for language_code, language_name in LANGUAGES %}
        {% get_language_info for language_code as lang %}

        {% language language_code %}
            <a href="{% pageurl page.localized %}" rel="alternate" hreflang="{{ language_code }}">
                {{ lang.name_local }}
            </a>
        {% endlanguage %}
    {% endfor %}

Let's break this down too:

.. code-block:: html+Django

    {% for language_code, language_name in LANGUAGES %}
        ...
    {% endfor %}

This ``for`` block iterates through all of the configured languages on the site.
The ``LANGUAGES`` variable comes from the ``django.template.context_processors.i18n``
context processor.

.. code-block:: html+Django

    {% get_language_info for language_code as lang %}

Does exactly the same as the previous example.

.. code-block:: html+Django

    {% language language_code %}
        ...
    {% endlanguage %}

This ``language`` tag comes from Django's ``i18n`` tag library. It changes the
active language for just the code contained within it.

.. code-block:: html+Django

    <a href="{% pageurl page.localized %}" rel="alternate" hreflang="{{ language_code }}">
        {{ lang.name_local }}
    </a>

The only difference with the ``<a>`` tag here from the ``<a>`` tag in the previous example
is how we're getting the page's URL: ``{% pageurl page.localized %}``.

All page instances in Wagtail have a ``.localized`` attribute which fetches the translation
of the page in the current active language. This is why we activated the language previously.

Another difference here is that if the same translated page is shared in two locales, Wagtail
will generate the correct URL for the page based on the current active locale. This is the
key difference between this example and the previous one as the previous one can only get the
URL of the page in its default locale.

API filters for headless sites
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

For headless sites, the Wagtail API supports two extra filters for internationalised sites:

 - ``?locale=`` Filters pages by the given locale
 - ``?translation_of=`` Filters pages to only include translations of the given page ID

For more information, see :ref:`apiv2_i18n_filters`.

Translatable snippets
^^^^^^^^^^^^^^^^^^^^^

You can make a snippet translatable by making it inherit from ``wagtail.core.models.TranslatableMixin``.
For example:

.. code-block:: python

    # myapp/models.py

    from django.db import models

    from wagtail.core.models import TranslatableMixin
    from wagtail.snippets.models import register_snippet


    @register_snippet
    class Advert(TranslatableMixin, models.Model):
        name = models.CharField(max_length=255)

The ``TranslatableMixin`` model adds the ``locale`` and ``translation_key`` fields to the model.

Making snippets with existing data translatable
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

For snippets with existing data, it's not possible to just add ``TranslatableMixin``,
make a migration, and run it. This is because the ``locale`` and ``translation_key``
fields are both required and ``translation_key`` needs a unique value for each
instance.

To migrate the existing data properly, we firstly need to use ``BootstrapTranslatableMixin``,
which excludes these constraints, then add a data migration to set the two fields, then
switch to ``TranslatableMixin``.

This is only needed if there are records in the database. So if the model is empty, you can
go straight to adding ``TranslatableMixin`` and skip this.

Step 1: Add ``BootstrapTranslatableMixin`` to the model
*******************************************************

This will add the two fields without any constraints:

.. code-block:: python

    # myapp/models.py

    from django.db import models

    from wagtail.core.models import BootstrapTranslatableMixin
    from wagtail.snippets.models import register_snippet


    @register_snippet
    class Advert(BootstrapTranslatableMixin, models.Model):
        name = models.CharField(max_length=255)

        # if the model has a Meta class, ensure it inherits from
        # BootstrapTranslatableMixin.Meta too
        class Meta(BootstrapTranslatableMixin.Meta):
            verbose_name = 'adverts'

Run ``python manage.py makemigrations myapp`` to generate the schema migration.

Step 2: Create a data migration
*******************************

Create a data migration with the following command:

.. code-block:: bash

    python manage.py makemigrations myapp --empty

This will generate a new empty migration in the app's ``migrations`` folder. Edit
that migration and add a ``BootstrapTranslatableModel`` for each model to bootstrap
in that app:

.. code-block:: python

    from django.db import migrations
    from wagtail.core.models import BootstrapTranslatableModel

    class Migration(migrations.Migration):
        dependencies = [
            ('myapp', '0002_bootstraptranslations'),
        ]

        # Add one operation for each model to bootstrap here
        # Note: Only include models that are in the same app!
        operations = [
            BootstrapTranslatableModel('myapp.Advert'),
        ]

Repeat this for any other apps that contain a model to be bootstrapped.

Step 3: Change ``BootstrapTranslatableMixin`` to ``TranslatableMixin``
**********************************************************************

Now that we have a migration that fills in the required fields, we can swap out
``BootstrapTranslatableMixin`` for ``TranslatableMixin`` that has all the
constraints:

.. code-block:: python

    # myapp/models.py

    from wagtail.core.models import TranslatableMixin  # Change this line

    @register_snippet
    class Advert(TranslatableMixin, models.Model):  # Change this line
        name = models.CharField(max_length=255)

        class Meta(TranslatableMixin.Meta):  # Change this line, if present
            verbose_name = 'adverts'

Step 4: Run ``makemigrations`` to generate schema migrations, then migrate!
***************************************************************************

Run ``makemigrations`` to generate the schema migration that adds the
constraints into the database, then run ``migrate`` to run all of the
migrations:

.. code-block:: bash

    python manage.py makemigrations myapp
    python manage.py migrate

When prompted to select a fix for the nullable field 'locale' being changed to
non-nullable, select the option "Ignore for now" (as this has been handled by the
data migration).


Translation workflow
--------------------

As mentioned at the beginning, Wagtail does not supply any built-in user interface
or external integration that provides a translation workflow. This has been left
for third-party packages to solve.

Wagtail Localize
^^^^^^^^^^^^^^^^

As part of the initial work on implementing internationalisation for Wagtail core,
we also created a translation package called ``wagtail-localize``. This supports
translating pages within Wagtail, using PO files, machine translation, and external
integration with translation services.

Github: https://github.com/wagtail/wagtail-localize

Alternative internationalisation plugins
========================================

Before official multi-language support was added into Wagtail, site implementors
had to use external plugins. These have not been replaced by Wagtail's own
implementation as they use slightly different approaches, one of them might
fit your use case better:

- `Wagtailtrans <https://github.com/wagtail/wagtailtrans>`_
- `wagtail-modeltranslation <https://github.com/infoportugal/wagtail-modeltranslation>`_

For a comparison of these options, see AccordBox's blog post
`How to support multi-language in Wagtail CMS <https://www.accordbox.com/blog/how-support-multi-language-wagtail-cms/>`_.

Wagtail admin translations
==========================

The Wagtail admin backend has been translated into many different languages. You can find a list of currently available translations on Wagtail's `Transifex page <https://www.transifex.com/torchbox/wagtail/>`_. (Note: if you're using an old version of Wagtail, this page may not accurately reflect what languages you have available).

If your language isn't listed on that page, you can easily contribute new languages or correct mistakes. Sign up and submit changes to `Transifex <https://www.transifex.com/torchbox/wagtail/>`_. Translation updates are typically merged into an official release within one month of being submitted.

Change Wagtail admin language on a per-user basis
=================================================

Logged-in users can set their preferred language from ``/admin/account/``.
By default, Wagtail provides a list of languages that have a >= 90% translation coverage.
It is possible to override this list via the :ref:`WAGTAILADMIN_PERMITTED_LANGUAGES <WAGTAILADMIN_PERMITTED_LANGUAGES>` setting.

In case there is zero or one language permitted, the form will be hidden.

If there is no language selected by the user, the ``LANGUAGE_CODE`` will be used.


Changing the primary language of your Wagtail installation
==========================================================

The default language of Wagtail is ``en-us`` (American English). You can change this by tweaking a couple of Django settings:

 - Make sure `USE_I18N <https://docs.djangoproject.com/en/stable/ref/settings/#use-i18n>`_ is set to ``True``
 - Set `LANGUAGE_CODE <https://docs.djangoproject.com/en/stable/ref/settings/#std:setting-LANGUAGE_CODE>`_ to your websites' primary language

If there is a translation available for your language, the Wagtail admin backend should now be in the language you've chosen.