What it is
hreflang uses ISO language and optional region codes. A wrong code, for example a country code where a language is expected, makes the annotation invalid and ignored. Wrong ISO codes. Invalid annotations are ignored. Use valid ISO 639-1 language + ISO 3166-1 region codes.
Why does invalid hreflang language/region code matter for AI search?
Invalid annotations are ignored.
How do you fix it?
Use valid ISO 639-1 language + ISO 3166-1 region codes.
How do you find it on your site?
- List the hreflang values in use.
- Validate each against ISO 639-1 language and ISO 3166-1 region codes.
- Correct any invalid combinations, such as en-UK which should be en-GB.
- Re-validate the set.
Which ranking and citation factors does it touch?
An invalid code is dropped, so that version loses its routing signal. Correct codes are essential for hreflang to apply.
What is the impact?
Medium-high. Direct.
What is the evidence?
Use valid language/region codes for hreflang. Google Search Central, Tell Google about localized versions (hreflang)
Sources
Frequently asked questions about invalid hreflang language/region code
What does "Invalid hreflang language/region code" mean?
Wrong ISO codes.
How do you fix invalid hreflang language/region code?
Use valid ISO 639-1 language + ISO 3166-1 region codes.