User locale on the site, where to store?

Question

Computer networks

Let's say there is a site with multilingual support, a user came in and chose his native locale or close to it.
Where to store the user's choice?
In sessions, or as part of the address example.com/ru/products/1234
Or in the GET parameter ?locale=ru
The subdomain name is not considered, as it is taken for other needs.
What other ideas do you have, pros and cons of different approaches?

Answer 1

Convenient for search engines www.site.ru/en www.site.ru/de

Answer 2

Familiar seo experts say that it is absolutely right to have different domains for different languages.

Answer 3

Why does the user need to select manually? When entering the site, the system itself will determine and set the desired language, and if the user is not satisfied with the choice, then ?lang=ru(ua, en, etc.) and save his choice in a cookie.