Can I use custom language / country code combinations in hreflang?

Question

I\'m internationalizing a large website in 14 languages.

I have found that some of the language/countries we want to target do not have lang-cc entries in various li

Answer 1

There is no list of "valid" combinations, as nobody can (nor should!) define which languages are spoken in which regions, or which linguistic variations exist.

HTML5 defines which content the hreflang attribute can have:

• hreflang for a/area
• hreflang for link

On Webmasters SE, I explained what this means (for the lang attribute, but it’s the same for hreflang): my answer to "Where do I get a list of attribute 'lang' values - what standard covers this, for SEO optimization?"

As you see, you only have to follow the rules from BCP 47 and choose tags from the Language Subtag Registry.

Thus da-GL is a valid value for hreflang/lang:

1. da is the subtag for the language Danish
2. - is the subtag separator
3. GL is the subtag for the region Greenland