Localizing and internationalizing an extension

Particularly in business relationships, there is often the need to build a website in more than one language. Therefore, the translation of the website content needs to be completed, but the extensions used must also be available in multiple languages.

The configuration options for localization inside TYPO3 are versatile. You will find a comprehensive description of all concepts and options in the Frontend Localization Guide (https://docs.typo3.org/typo3cms/FrontendLocalizationGuide/). For the following sections, we assume a correct configuration of the localization, which is normally done in the site configuration.

The frontend language selection is carried out with a URL parameter (linkVars = L). Important is the definition of the UID of the language (sys_language_uid = 0) and the language key of the language (language = default). When the URL of the website contains the parameter L=1, the output occurs in German; if the parameter is not set, the output of the website occurs in the default language (in our example in English).

In the next section, we start with the translation of static text like captions of links in templates. After this, we go to translate the content of extensions, thus the domain objects. Finally, we explain how you can adjust the date formats following the date conventions in a particular country.

Multi-language templates

When you style the output of your extension using Fluid, you often have to localize particular terms or maybe short text in the templates. In the following sample template of the blog example displays a single blog post with its comments there are some constant terms:

<p>By: {post.author.fullName}</p>
<p>{post.content -> f:format.nl2br()}</p>

<f:for each="{post.comments}" as="comment">
  {comment.content -> f:format.nl2br()}


The template is a little bit simplified and reduced to the basic.

First of all, the text “By:” in front of the author of the post is hardcoded in the template and the caption “Comments”. For the use of the extension on an English website, this is no problem, but if you want to use it on a German website, the texts “By” and “Comments” would be displayed instead of “Von” and “Kommentare”. To make such text exchangeable, it has to be removed from the template and inserted in a language file. Every text which is to be translated is given an identifier that can be inserted in the template later. Table 9-1 shows the identifier used in the sample and their translations into German and English.

Table 9-1: The texts how we want to translate them

Identifier English German
author_prefix By: Von:
comment_header Comments Kommentare

In TYPO3 (and in Extbase), the language file in which the translated terms are stored is named locallang.xlf. It should contain all terms that have to be translated, in our example “By:” and “Comments”, and their translations. Using Extbase the the file locallang.xlf must reside in the folder Resources/Private/Language/. To localize the above terms we create the locallang.xlf file the following way:

 <?xml version="1.0" encoding="UTF-8"?>
 <xliff version="1.0" xmlns="urn:oasis:names:tc:xliff:document:1.1">
    <file source-language="en" datatype="plaintext" original="messages" date="2011-10-18T18:20:51Z" product-name="my-ext">
            <trans-unit id="author_prefix">
            <trans-unit id="comment_header">


The TYPO3 Core API describes in detail the construction of the locallang.xlf file: XLIFF Format.

Now the placeholder for the translated terms must be inserted into the template. To do this, Fluid offers the ViewHelper f:translate. In this ViewHelper, you give the identifier of the term to be inserted as argument key and the ViewHelper inserts either the German or the English translation according to the current language selection:

<f:translate key="comment_header" />
<!-- or -->
{f:translate(key: 'comment_header')}


The used language is defined in the TypoScript template of the website. By default, the English texts are used; but when with the TypoScript setting, config.language = de you can set the used language to german, for example.

To implement a language selection, normally, TypoScript conditions are used. These are comparable with an if/else block

[globalVar = GP:L = 1]
   config.language = de
   config.language = default

When the URL of the website contains a parameter L=1, then the output is in German; if the parameter is not set, the output is in the default language English.

With the use of complex TypoScript conditions, the language selection could be set to depend on the forwarded language of the browser.

By replacing all terms of the template with the translate ViewHelper we could fit the output of the extension to the currently selected language. Here we have a look at the Fluid template for the output of the blog posts, now without the hardcoded English terms:

<p><f:translate key="author_prefix"> {post.author.fullName}</p>
<p>{post.content -> f:format.nl2br()}</p>
<h3><f:translate key="comment_header"></h3>
<f:for each="{post.comments}" as="comment">
   {comment.content -> f:format.nl2br()}


Sometimes you have to localize a string in the PHP code, for example inside of a controller or a ViewHelper. In that case you can use the static method \TYPO3\CMS\Extbase\Utility\LocalizationUtility::translate($key, $extensionName). This method requires the localization key as the first and the extension’s name as the second parameter. Then the corresponding text in the current language will be loaded from this extension’s locallang.xlf file .

Output localized strings using sprintf

In the above example, we have outputted the blog post author’s name simply by using {blog.author.fullName}. Many languages have special rules on how names are to be used - especially in Thailand, it is common to only show the first name and place the word “Khan” in front of it (which is a polite form). We want to enhance our template now as far as it can to output the blog author’s name according to the current language. In German and English, this is the form “first name last name” and in Thai “Khan first name”.

Also, for these use cases, the translate ViewHelper can be used. With the aid of the array arguments, values can be embedded into the translated string. To do this, the syntax of the PHP function sprintf is used.

If we want to implement the above example, we must assign the first name and the last name of the blog author separate to the translate ViewHelper:

<f:translate key="name" arguments="{1:post.author.firstName, 2: post.author.lastName}" />

How should the corresponding string in the locallang.xml file looks like? It describes in which position the placeholder is to be inserted. For English and German it looks like this:

<label index="name">%1$s %2$s</label>

Important are the placeholder strings %1$s and %2$s. These will be replaced with the assigned parameters. Every placeholder starts with the % sign, followed by the position number inside the arguments array, starting with 1, followed by the $ sign. After that, the usual formatting specifications follow - in the example, it is the data type string (s). Now we can define for Thai that “Khan” followed by the first name should be output:

<label index="name">Khan %1$s</label>


The keys in the argument array of the ViewHelper have no relevance. We recommend to give them numbers like the positions (starting with 1), because it is easily understandable.


For a full reference of the formatting options for sprintf you should have a look at the PHP documentation: http://php.net/manual/de/function.sprintf.php.

Changing localized terms using TypoScript

If you use an existing extension for a customer project, you sometimes find out that the extension is insufficient translated or that the translations have to be adjusted. TYPO3 offers the possibility to overwrite the localization of a term by TypoScript. Fluid also supports this.

If, for example, you want to use the text “Remarks” instead of the text “Comments”, you have to overwrite the identifier comment_header for the English language. For this, you can add the following line to your TypoScript template:

plugin.tx_blogexample._LOCAL_LANG.default.comment_header = Remarks

With this, you will overwrite the localization of the term comment_header for the default language in the blog example. So you can adjust the translation of the texts like you wish, without changing the locallang.xml file.

Until now, we have shown how to translate a static text of templates. Of course, an extension’s data must be translated according to the national language. We will show this in the next section.

Multi-language domain objects

With TYPO3, you can localize the data sets in the backend. This also applies to domain data because they are treated as “normal” data sets in the TYPO3 backend. To make your domain objects translatable, you have to create additional fields in the database and tell TYPO3 about them. The class definitions must not be changed. Let’s look at the required steps based on the blog class of the blog example. TYPO3 needs three additional database fields which you should insert in the ext_tables.sql file:

CREATE TABLE tx_blogexample_domain_model_blog (
    --  ...
    sys_language_uid int(11) DEFAULT '0' NOT NULL,
    l10n_parent int(11) DEFAULT '0' NOT NULL,
    l10n_diffsource mediumblob NOT NULL,
    -- ...

You are free to choose the names of the database fields, but the names we use here are common in the world of TYPO3. In any case, you have to tell TYPO3 which name you have chosen. This is done in the ctrl section of the TCA configuration file Configuration/TCA/tx_blogexample_domain_model_blog.php


return [
    'ctrl' => [
        // ...
        'languageField' => 'sys_language_uid',
        'transOrigPointerField' => 'l10n_parent',
        'transOrigDiffSourceField' => 'l10n_diffsource',
        // ...

The field sys_language_uid is used for storing the UID of the language in which the blog is written. Based on this UID Extbase choose the right translation depending on the current site. In the field l10n_parent the UID of the original blog created in the default language, which the current blog is a translation of. The third field, l10n_diffsource contains a snapshot of the source of the translation. This snapshot is used in the backend for the creation of a differential view and is not used by Extbase.

In the section columns of the TCA you have to configure the fields accordingly. The following configuration adds two fields to the backend form of the blog: one field for the editor to define the language of a data record and one field to select the data record the translation relates to.


return [
    // ...
    'types' => [
        '1' => ['showitem' => 'l10n_parent , sys_language_uid, hidden, title,
                    description, logo, posts, administrator'],
    'columns' => [
        'sys_language_uid' => [
            'exclude' => 1,
            'label' => 'LLL:EXT:core/Resources/Private/Language/locallang_general.php:LGL.language',
            'config' => [
                'type' => 'select',
                'foreign_table' => 'sys_language',
                'foreign_table_where' => 'ORDER BY sys_language.title',
                'items' => [
        'l10n_parent' => [
            'displayCond' => 'FIELD:sys_language_uid:>:0',
            'exclude' => 1,
            'label' => 'LLL:EXT:core/Resources/Private/Language/locallang_general.php:LGL.l10n_parent',
            'config' => [
              'type' => 'select',
              'items' => [
                  ['', 0],
              'foreign_table' => 'tx_blogexample_domain_model_blog',
              'foreign_table_where' => 'AND tx_blogexample_domain_model_blog.uid=###REC_FIELD_l10n_parent### AND tx_blogexample_domain_model_blog.sys_language_uid IN (-1,0)',
        'l10n_diffsource' => [
            'config' => [
              'type' =>'passthrough'
        // ...

With it, the localization of the domain object is already configured. By adding &amp;L=1 to the URL, the language of the frontend will be changed to german. If there is an existing translation of a blog, it will be shown. Otherwise, the blog is output in the default language.


You can control this behavior. If you configure the site to strict language mode, then only those objects are shown, which really have content in the frontend language. More information for this you will find in the Frontend Localization Guide of the Core Documentation.

How TYPO3 handles the localization of content offers two important specific features: The first is that all translations of a data record respectively a data record that is valid for all languages (UID of the language is 0 or -1) will be “added” to the data record in the default language. The second special feature is that always the UID of the record in the default language is bound for identification although the translated data record in the database table has another UID. This conception has a serious disadvantage: If you want to create a data record for a language with no data record in the default language, you have to create the latter before. But with what content?

Let’s have an example for illustration: You create a blog in the default language English (=default). It is stored in the database like this:

Example database content
uid:              7 (given by the database)
title:            "My first Blog"
sys_language_uid: 0 (selected in backend)
l10n_parent:      0 (no translation original exists)

After a while, you create a German translation in the backend. In the database the following record is stored:

Example database content
uid:              42 (given by the database)
title:            "Mein erster Blog"
sys_language_uid: 1 (selected in backend)
l10n_parent:      7 (selected in backend respectively given automatically)

A link that references the single view of a blog looks like this:


By adding &amp;L=1 we referencing now the German version:


Notice that the given UID in tx_blogexample_pi1[blog]=7 is not changed. There is not UID of the data record of the german translation (42). This has the advantage that only the parameter for the language selection is enough. Concurrently it has the disadvantage of a higher administration effort during persistence. Extbase will do this for you by carrying the UID of the language of the domain model and the UID of the data record in which the domain data is effectively stored as “hidden” properties of the AbstractDomainObject internally. In Table 9-2, you find for different actions in the frontend the behavior of Extbase for localized domain objects.

Table 9-2: Behavior of Extbase for localized domain objects in the frontend.

  No parameter L given, or L=0 L=x (x>0)
Display (index, list, show) Objects in the default language (sys_language_uid=0) respectively object for all languages (sys_language_uid=-1) are shown The objects are shown in the selected language x. If an object doesn’t exist in the selected language the object of the default language is shown (except by sys_language_mode=strict)
Editing (edit, update) Like displaying an object. The domain data is stored in the “translated” data record, in the above example in the record with the UID 42.
Creation (new, create) Independent of the selected frontend language the data is stored in a new record in whose field sys_language_uid the number 0 is inserted.

Extbase also supports all default functions of the localization of domain objects. It has its limits when a domain object should be created exclusively in a target language. Especially when no data record exists in the default language.

Localization of date output

It often occurs that a date or time must be displayed in a template. Every language area has its own convention on how the date is to be displayed: While in Germany, the date is displayed in the form Day.Month.Year, in the USA the form Month/Day/Year is used. Depending on the language, the date must be formatted different.

Generally the date or time is formatted by the format.date ViewHelper:

<f:format.date date="{dateObject}" format="d.m.Y" />
<!-- or -->
{dateObject -> f:format.date(format: 'd.m.Y')}

The date object {dateObject} is displayed with the date format given in the parameter format. This format string must be in a format that is readable by the PHP function date() and declares the format of the output. Table 9-3 shows some important placeholders.

Table 9-3: Some place holder of date.

Format character Description Example
d Day of the month as number, double-digit, with leading zero 01 … 31
m Month as number, with leading zero 01 … 12
Y Year as number, with 4 digits 2011
y Year as number, with 2 digits 11
H Hour in 24 hour format 00 … 23
i Minutes, with leading zero 00 … 59

But the ViewHelper has to be configured differently. Depending on the language area, which is controlled by the language of the user, another format string should be used. Here we combine the format.date ViewHelper with the translate ViewHelper which you got to know in the section “Multi-language templates”.

<f:format.date date="{dateObject}" format="{f:translate(key: 'date_format')}" />

Then you can store another format string for every language in the locallang.xml file, and you can change the format string via TypoScript if needed. This method to translate the content you got to know in the section “Multi-language templates”.


There are other formatting ViewHelpers for adjusting the output of currencies or big numbers. These ViewHelpers all starts with format. You can find an overview of these ViewHelpers in Appendix C. These ViewHelpers can be used like the f:format.date ViewHelper you have just learned.

In this section, you have learned how you can translate and localize an extension. First, we have worked on the localization of single terms in the template. After this, we had a look at the content of the extension. Finally, the customization of date information for country-specific formats where explained. In the next section, you will see how constraints of the domain objects can be preserved.

TYPO3 v9 and higher

Starting with version 9, Extbase renders the translated records in the same way TypoScript rendering does.


In previous version the behaviour was controllable by the feature switch consistentTranslationOverlayHandling which has been removed in newer versions.

  1. Setting Typo3QuerySettings->languageMode does not influence how Extbase queries records. The language mode is used by the core to decide what to do when a page is not translated to the given language (display 404 or try page with a different language). Users who used to set Typo3QuerySettings->languageMode to strict should use Typo3QuerySettings->setLanguageOverlayMode('hideNonTranslated') to get translated records only.

  2. Setting Typo3QuerySettings->languageOverlayMode to true makes Extbase fetch records from default language and overlay them with translated values. So, e.g., when a record is hidden in the default language, it will not be shown. Also, records without translation parents will not be shown. For relations, Extbase reads relations from a translated record (so it’s not possible to inherit a field value from translation source) and then passes the related records through $pageRepository->getRecordOverlay(). So, e.g., when you have a translated tt_content with FAL relation, Extbase will show only those sys_file_reference records which are connected to the translated record (not caring whether some of these files have l10n_parent set).

  3. Setting Typo3QuerySettings->languageOverlayMode to false makes Extbase fetch aggregate root records from a given language only. Extbase will follow relations (child records) as they are, without checking their sys_language_uid fields, and then it will pass these records through $pageRepository->getRecordOverlay(). This way, the aggregate root record’s sorting and visibility don’t depend on default language records. Moreover, the relations of a record, which are often stored using default language uids, are translated in the final result set (so overlay happens).

    For example: Given a translated tt_content having relation to 2 categories (in the mm table translated tt_content record is connected to category uid in default language), and one of the categories is translated. Extbase will return a tt_content model with both categories. If you want to have just translated category shown, remove the relation in the translated tt_content record in the TYPO3 backend.

Note that by default Typo3QuerySettings uses the site language configuration. So you need to change Typo3QuerySettings manually only if your Extbase code should behave different than other tt_content rendering.

Setting setLanguageOverlayMode() on a query influences only fetching of the aggregate root. Relations are always fetched with setLanguageOverlayMode(true).

When querying data in translated language, and having setLanguageOverlayMode(true), the relations (child objects) are overlaid even if the aggregate root is not translated. See QueryLocalizedDataTest->queryFirst5Posts().

The following examples show how to query data in Extbase in different scenarios, independent of the global TS settings:

  1. Fetch records from the language uid=1 only, with no overlays.
$querySettings = $query->getQuerySettings();
  1. Fetch records from the language uid=1, with overlay, but hide non-translated records
$querySettings = $query->getQuerySettings();


Domain models have a main identifier uid and two additional properties _localizedUid and _versionedUid. Depending on whether the languageOverlayMode mode is enabled (true or 'hideNonTranslated') or disabled (false), the identifier contains different values. When languageOverlayMode is enabled, then the uid property contains the uid value of the default language record, the uid of the translated record is kept in the _localizedUid.

Context Record in language 0 Translated record
Database uid:2 uid:11, l10n_parent:2
Domain object values with languageOverlayMode enabled uid:2, _localizedUid:2 uid:2, _localizedUid:11
Domain object values with languageOverlayMode disabled uid:2, _localizedUid:2 uid:11, _localizedUid:11

See tests in extbase/Tests/Functional/Persistence/QueryLocalizedDataTest.php.

The $repository->findByUid() (or $persistenceManager->getObjectByIdentifier()) method takes current rendering language into account (e.g. L=1). It does not take defaultQuerySetting set on the repository into account. This method always performs an overlay. Values in braces show previous behavior (disabled flag) if different than current.

The bottom line is that with the feature flag on, you can now use findByUid() using translated record uid to get translated content independently from language set in the global context.

    L=0 L=1
repository method property Overlay No overlay Overlay No overlay
findByUid(2) title Post 2 Post 2 Post 2 - DK Post 2 - DK
  uid 2 2 2 2
  _localizedUid 2 2 11 11
findByUid(11) title Post 2 - DK (Post 2) Post 2 - DK (Post 2) Post 2 - DK Post 2 - DK
  uid 2 2 2 2
  _localizedUid 11 (2) 11 (2) 11 11


Note that $repository->findByUid() internally sets respectSysLanguage(false) so it behaves differently than a regular query by an uid like $query->matching($query->equals('uid', 11)); The regular query will return null if passed uid doesn’t match the language set in the $querySettings->setLanguageUid() method.

Filtering & sorting

When filtering by an aggregate root property like Post->title, both filtering and sorting take translated values into account, and you will get correct results, same with pagination.

When filtering or ordering by a child object property, Extbase does a left join between the aggregate root table and the child record table. Then the filter is applied as where clause. This means filtering or ordering by a child record property only takes values from child records whose uids are stored in the database (in most cases, its default language record). See TranslationTest::fetchingTranslatedPostByBlogTitle()

This limitation also applies to Extbase, with the feature flag being disabled.

Summary of the important code changes compared to previous versions

  1. DataMapper gets a Query as a constructor parameter. This allows to use the aggregate root’s QuerySettings (language) when fetching child records/relations. See DataMapper->getPreparedQuery method.
  2. DataMapper is passed to LazyLoadingProxy and LazyObjectStorage, so the settings don’t get lost when fetching data lazily.
  3. Query object gets a new property parentQuery which is useful to detect whether we’re fetching the aggregate root or a child object.
  4. Extbase model for FileReference uses _localizedUid for fetching OriginalResource
  5. DataMapper forces child records to be fetched using setLanguageOverlayMode(true).
  6. When getRespectSysLanguage is set, DataMapper uses aggregate root’s language to overlay child records to the correct language.
  7. The where clause used for finding translated records in overlay mode (true, hideNonTranslated) has been fixed in version 9. It filters out the non translated records on the database side in case hideNonTranslated is set. It allows for filtering and sorting by translated values. See Typo3DbQueryParser->getLanguageStatement()

Most important known issues

  • The persistence session uses the same key for the default language record and the translation - Forge #59992
  • Extbase allows fetching deleted/hidden records - Forge #86307

For more information about rendering, please refer to the TypoScript reference.