If you have a business with multiple languages and markets, then internationalisation and hreflang implementation need to be top of your list.
Hreflang is a piece of code that lives on your page that tells Google and other search engines "this is the English US version, this other URL is is the English Canada version, this other URL is the French Canada version", and so forth. Your SEO resource will be able to advise you on the exact issues that might be presenting themselves and how to implement hreflang successfully.
In this case with a global luxury eCom shop website, I had 2 different subdomains that were practically identical, except for the currency. We had a subdomain for US traffic, and we had a subdomain for Canada (CA) traffic. The way that this was setup meant that we had to keep both subdomains separate and try to stop the US version ranking in Canada, and vice-versa.
This website did have hreflang set up, however the values in the code were completely incorrect and unfortunately made the code useless.
This is why it is very important that you have a technical SEO audit and an SEO resource on hand to be able to catch these issues - from a development standpoint, they had already implemented hreflang, so it was not seen as a weakness and a reason that we were seeing cannibalisation of traffic from each subdomain when they were ranking in the wrong market.
Additionally, when Google sees that you have two duplicate sites, it will generally see one of them as a copy, and favour the other one. On top of this, Google may also hold back the one website it has favoured, because it has duplicate content too.
Essentially, we prevent both subdomains from being able to grow in SEO traffic as they otherwise would have done if they had correctly implemented hreflang.
Check out the results after 1 and a half months:
This resulted in:
US Subdomain gained +30% more US SEO traffic and +36% more US SEO impressions
CA Subdomain gained +43% more CA SEO traffic and +38% more CA SEO impressions
The issues that were surrounding the hreflang were inhibiting the SEO growth of both subdomains, and now they are able to function independently rather than steal from each other.
This is vital if your website is has different URLs for different markets, especially in eCommerce.
If you would like your internationalisation reviewed, take a look at my SEO services, and reach out for a free initial conversation.