Invalid hreflang language code

Error severity, in the Hreflang tab

Why it matters

Language codes must be ISO 639-1, optionally with an ISO 3166-1 region (en, en-GB).

How to fix it

Correct the code (for example 'en-UK' is invalid; use 'en-GB').

How Crawlune finds it

Crawlune flags Invalid hreflang language code automatically on every crawl and lists the affected URLs under the Hreflang tab, where you can filter, inspect each page and export the list to CSV. The free version crawls up to 550 URLs with every check enabled.