I think representing the default language in the URL is the better choice.
Pros:
- If you decide to change the default language, you don’t have to change your URLs.
- Consistency.
- It allows you to redirect from
/ based on the visitor’s language preference.
- It’s a signal that your site is available in multiple languages.
- It’s easier for users that want to change the language from the URL.
- It allows users of external search engines to search for pages in the default language only (
site:example.com/en/; where site:example.com/ would find pages in all languages).
Cons:
I can’t think of any reasons not to include the default language’s code in the URL.
