The interface is in English, however you can build your eCRFs in any language. The survey data entry interface is available in English, Dutch, French, German, Spanish, Portuguese and Italian. The survey translations apply to buttons and messages. Creating a translated version of the actual questions in the survey will need to be done by the person creating the questionnaire. The default language of the survey interface will be set based on browser settings, for example Dutch languages will be set on browsers set to this language. English on all others.
Learn more about Testing your survey.