As you'd likely know, SEO is a whole topic in itself, and there's no real 'perfect' solution - just a set I assumptions we make about how search will view out pages. Below is a clarification on how our Bilingual Theme works from an SEO point of view, why we chose that route, and how to get the best out of it.
1. How does the theme handle SEO?
2. Why this approach?
Because, with the way Shopify’s inventory management works, if you wanted to have one unique URL for each language, you’d have to maintain and manage a double inventory. This would be a logistical nightmare. Essentially, you would need to have two versions of every product – eg one called ’4-ports-switch’ and another called ‘commutateur-4-ports’, and Shopify would treat these as completely separate products.
Our system will allow you to have only one set of products (much easier), and everything will be displayed on the one URL.
3. What should I add in my SEO Tags?
Our Theme is fully integrated with Shopify 2's SEO fields. You'll see these on your products, pages, and blog posts in the Shopify Admin. You can enter text there just as you would with any other theme, for the fields like Page Title, Description, and URL.
Since we only have one text field for both languages (not one each), you'll need to take care to include SEO information for BOTH languages in the one place.
For instance, in page titles, I usually use "Language1 | Language2" so that google can see both, and I'd put your PRIMARY target language first. For example, if your page was in English and Spanish, and English was your primary target: "My text with keywords|Mi texto con palabras claves".