Hreflang is the most fragile piece of international SEO. One wrong country code and Google shows the Russian version to a user in Canada. Missing reciprocal link and both versions compete for the SERP. The tool walks the hreflang markup on the given URL, validates codes against ISO 639-1 + ISO 3166-1, follows each alternate link, and records whether each has a reciprocal hreflang back to the source page.
What the check finds
- Wrong language / country codes (ru_RU instead of ru-RU — a common bug).
- Missing reciprocal links (A points to B, B does not point back to A).
- Missing x-default — Google uses it as the fallback.
- Hreflang pointing to 404 or a redirect — engines ignore the markup.
- Conflict between hreflang in HTML, HTTP header, and sitemap.