Deprecation: #99882 - Site language "typo3Language" setting

See forge#99882


A language configuration defined for a site has had various settings, one of them being typo3Language. The setting is used to define the language key which should be used for fetching the proper XLF file (such as de_AT.locallang.xlf).

Since TYPO3 v12 it is unnecessary to set this property in the site configuration and it is removed from the backend UI. The information is now automatically derived from the locale setting of the site configuration.

The previous value "default", which matched "en" as language key is now unnecessary as "default" is now a synonym for "en".

As a result, the amount of options in the user interface for integrators is reduced.


An administrator cannot select a value for the typo3Language setting anymore via the TYPO3 backend. If a custom value is required, the site configuration needs to be manually edited and the typo3Language setting needs to be added.

If this is the case, please file a bug report in order to give the TYPO3 development team feedback on what use case is required.

However, saving a site configuration via the TYPO3 backend will still keep the typo3Language setting so no values will be lost.

Affected installations

TYPO3 installations created before TYPO3 v12.3.


No migration is needed as the explicit option is still evaluated. It is however recommended to check if the setting is really necessary.


  1. If typo3Language: "default" and locale: "en_US.UTF-8", the setting can be removed.
  2. If typo3Language: "pt_BR" and locale: "pt_BR.UTF-8", the setting can be removed.
  3. If typo3Language: "de" and locale: "de_AT.UTF-8" , the setting can be removed, plus the label files check for de_AT.locallang.xlf and de.locallang.xlf as fallback when accessing a translated label.
  4. If typo3Language: "pt_BR" and locale: "de_DE.UTF-8" it is likely a misconfiguration in the setup, and should be analyzed if the custom value is really needed.