How to set up site indexing with automatic language detection?

Question

Search Engine Optimization

There is a site where absolutely on all pages the language is determined by the browser settings, namely by the header Accept-Language , that is, if the page on the site has the address example.com/about , then the link will be the same for both the Russian-speaking user and the English-speaking one. Although the help of Google and Yandex suggests separating versions of pages in different languages ​​by adding the language code to the URL, I don’t want to add the language code.
The site has already been indexed and in the search results all pages are now displayed in English, regardless of whether the site came across to a Russian-speaking or English-speaking user. But how to set up indexing so that if the site comes across in the search results for a Russian-speaking user, then the text is displayed in Russian, and for an English-speaking user, respectively, in English?

Answer 1

I think hreflang will help
https://yandex.ru/support/webmaster/yandex-indexin...
https://support.google.com/webmasters/answer/18907...

Answer 2

hreflang and more.

Answer 3

It is for people that the language changes, but not for Googlebot. Dividing the site into subdomains or adding parameters to the URL is necessary for Google or Yandexbot so that they can correctly index pages in different languages.