Feature: #86913 - Automatic support for language files of languages with region suffix

See forge#86913


TYPO3's native support for label files - that is: translatable text for system labels such as from plugins, and for texts within TYPO3 backend - supports over 50 languages. Languages are identified by their "language key" of the ISO 639-1 standard, which also allows the use of a region-specific language. This happens mostly in countries/regions that have a variation of the language, such as "en-US" for American English, or "de-CH" for the German language in Switzerland.

To support these region-specific language keys, which are composed of ISO 639-1 and ISO 3166-1 and separated with -, TYPO3 integrators had to configure the additional language manually to translate region-specific terms.

Common examples are "Behavior" (American English) vs. "Behaviour" (British English), or "Offerte" (Swiss German) vs. "Angebot" (German), where all labels except a few terms should stay the same.


TYPO3 now allows integrators to use a custom label file with the locale prefix de_CH.locallang.xlf in an extension next to de.locallang.xlf and locallang.xlf (default language English).

When integrators then use de-CH within their site configuration, TYPO3 first checks if a term is available in the translation file de_CH.locallang.xlf, and then automatically falls back to the non-region-specific de translation file de.locallang.xlf without any further configuration to TYPO3.

Previously, such region-specific locales had to be configured via:

$GLOBALS['TYPO3_CONF_VARS']['SYS']['localization']['locales']['user'] = [
    'de-CH' => 'German (Switzerland)',

The same fallback functionality also works when overriding labels via TypoScript:

plugin.tx_myextension._LOCAL_LANG.de = Angebot
plugin.tx_myextension._LOCAL_LANG.de-CH = Offerte