Why is the "Country" field/question in my form shown in different languages to users?

With Prefinery's customizable signup form, besides the email address you can add other questions/fields like Country which is a dropdown with a preset selection of all countries. 

When used, the Country dropdown will auto-localized to the end-users' first preferred language, as sent by the "Accept-Language" HTTP header. 

The user's browser and/or OS will set the list of preferred language(s) and we'll use the first like as shown above. If their language is one for which we don't have a translation, then we fall back on English. There's not a way nor setting to change this behavior anywhere in the project. 

Below is an example of the Country field with all dropdown options in English: 

If the preferred language was Spanish for example, then the Country dropdown would look like as follows: