With Sharing-Data, the same questionnaire can be published in several different language even if the answers will be analysed all together. The questionnaire language is the language of your questions (and, hopefully, of the answers you will get). This language is completely free as you are the one who write the questions and translate them. The interface language is the language of the alert messages. These are the contextual messages that the respondents will get some times. For instance, if a mandatory question has not been answered and that the respondent try to validate his questionnaire, Sharing-Data will tell him that the questionnaire could not be validated and gives the reason why. The interface language is therefore pre-defined. Sharing-Data comes with a set of interface language: French, English, German, Spanish, Portuguese, Chinese (Mandarin), Japanese, Russian and Korean. For each of these languages, you can customize the messages. You can also, of course, add your own languages. To do so, please see the tutorial about localizing your questionnaire.