While translating our Magento store, we can never be too careful when it comes to duplicate content. Essentially, what we are doing is duplicating our Magento installation and then translating the same pages into different languages.
In order to specifically inform search engines such as Google and Yandex of the locations of our translated pages, we should use the rel="alternate" hreflang="x" tag.
This tag lets search engines know the exact location and intended audience of our translated pages. There are two implementations of this tag; one is with meta information stored in the <head> tag per page and the other is through the XML sitemap.
The correct method for using the rel="alternate" hreflang="x" tag is to include a copy of it within our <head> area for each and every translated version of our page. The following is an example of that:
<-- default to our primary website language version of this pageusing x-default --> ...