You can create your own plug to set locale for you, but a easy way is to use set_locale.

So in your router you define your basic locale and scopes.

router.ex

...
  pipeline :app do
    ...
    plug SetLocale, gettext: MyApp.Gettext, default_locale: "en"
    ...
  end
...
  scope "/:locale", MyAppWeb do
    pipe_through [:browser, :app, :browser_session]
    get "/", PageController, :index
  end
...

This will add locale as a params to your controller.
At this point you have a locale (fr, en, any…), so it’s up to you to use (to translate with gettext) or not (to provide photos) inside your controller.

controller.ex

  def new(conn, params) do
    locale =
      params["locale"]
    ...
    conn
    |> render("new.html", changeset: changeset,
      locale: locale)
  end

As a note, there is a standard header (Accept-Language) passed in for the browser to request a locale, why not use that instead of encoding it into the path?

The header is nice as a default, but people might want so view a different language than the default one.

Exactly this. My browser sends a German request, and i do not bother for much resources, but when I hear some technical documentation, I prefer to read it in English as the quality of the text is usually better, as well as it’s usually more complete as well.

This is especially true when I’m browsing Microsoft documentation, which is partially translated by humans and by machines or simply leaving out complete paragraphs…

as a general approach I usually try to avoid hard coding locale params in the urls, I use the language header or a cookie if the user need to view the page in a different language

You might also find Cldr.Plug.SetLocale in the package ex_cldr useful. (I’m the author). It can:

1. Set locale for gettext and cldr (either or both)
2. Identify locale from the Accept-Languge header, the url, the session, a cookie or a query param or any combination in any priority

That’s good to guess the default locale, but if you are not using your own browser you will not want to have the same links open in a locale you do not know. Also, as I want the urls to be different based on the locale, this wouldn’t do (aside from “/”).

This looks like my first solution (I do use cldr’s setlocale in my pipeline btw).

But with

  scope "/:locale", MyAppWeb do
    pipe_through [:browser, :app, :browser_session]
    get "/", PageController, :index
  end

there is no way to define localised urls like get "/photos", PageController, :index and get "/pictures", PageController, :index, as both “/fr/pictures” and “/en/photos” would resolve and I do not want that.

When urls are not localised that’s a good possibility, until you travel and have to use browsers with chinese locale by default

@kip (I can’t reply to your post as I have 3 consecutive posts..)

I am using it for the root url in order to guess the locale! It works like a charm.

In order to make it to work with the url, I have to use the option “:path”, with a parameter name right? So as I cannot define my routes with a scope like scope "/:locale", MyAppWeb do, I cannot set this parameter name. It worked until I decided to have localised urls (UNLESS there is a way to restrict routes depending on the value of :locale (e.g. define get "/pictures", PageController, :index only when :locale == "en").

You can still have scopes / pipeplines with locale or not (/photos) in a correct order in your router. In my case I have one that dosen’t need (llike /) and other that check via plug the accepted one and redirect the user to default or available language (gettext).

example without pipeline / locale

  scope "/", MyAppWeb do
    pipe_through :browser
    get "/", Tracker.Controller, :index
  end