Rails I18N gives you a way to translate your views and easily switch between different languages. However, you still need to set the locale for each request, i.e. you have to choose a method to select the right locale for a request. This can be done in various ways, depending on how you perfer it to behave. Here are some examples.

1. by browser-setting
2. by toplevel domain
3. by subdomain
4. by manual selection