Except for some low level functions, TYPO3 CMS exclusively uses localizable strings for all labels displayed in the backend. This means that the whole user interface may be translated. The encoding is strictly UTF-8.

The default language is English, and the Core ships only with such labels (and so should extensions).

All labels are stored in XLIFF format, generally located in the Resources/Private/Language folder of an extension (old locations may still be found in some places).

The format, TYPO3 specific details and managing interfaces of XLIFF are outlined in detail in this chapter.

Label Access in PHP

In PHP, a typical call in the Backend to fetch a string in the language selected by a user looks like this:


getLanguageService() is a call to a helper method that accesses $GLOBALS['LANG']. In the Backend, the bootstrap parks an initialized instance of \TYPO3\CMS\Core\Localization\LanguageService at this place. This may change in the future, but for now the LanguageService can be reliably fetched from this global.


The ->sL() API does not apply a htmlspecialchars() call to the translated string. If the string is returned in a web context, it must be added manually.

If additional placeholders are used in a translation source, they must be injected, a call then typically looks like this:

// Text string in .xlf file has a placeholder:
// <trans-unit id="message.description.fileHasBrokenReferences">
//     <source>The file has %1s broken reference(s) but it will be deleted regardless.</source>
// </trans-unit>
sprintf($this->getLanguageService()->sL('LLL:EXT:core/Resources/Private/Language/locallang_core.xlf:message.description.fileHasBrokenReferences'), count($brokenReferences));

Various classes are involved in the localization process, with \TYPO3\CMS\Core\Localization\LanguageService providing the actual methods to retrieve a localized label. sL() loads a language file if needed first, and then returns a label from it (using a string with the LLL:EXT:... syntax as argument).

Extbase class \TYPO3\CMS\Extbase\Utility\LocalizationUtility is essentially a convenience wrapper around the \TYPO3\CMS\Core\Localization\LanguageService class, whose translate() method also takes an array as argument and runs PHP’s vsprintf() on the localized string. However, in the future it is expected this Extbase specific class will melt down and somehow merged into the core API classes to get rid of this duplication.