A web rule is that the same URL shouldn't provide different contents, even the same thing in different languages. To do so, the locale should be in the URL. However, some websites ignore that rule, Youtube for instance. So I'd like to understand a few things about that:
- Are there consequences if we ignore that rule for translation? (like SEO wise)
- What does Youtube do to avoid these consequences?
To give a context, I don't really want to use different URLs, I'd rather use the header Accept-language header, or a user setting if it exists. I'm using Symfony.