1.8 URL structure & internationalisationHighVerified
Invalid hreflang language/region code
What it is
Wrong ISO codes.
Why it matters
Invalid annotations are ignored.
How to fix it
Use valid ISO 639-1 language + ISO 3166-1 region codes.
Impact
Medium-high. Direct.
Evidence
Use valid language/region codes for hreflang. Google Search Central, Tell Google about localized versions (hreflang)