hreflang checker

Hreflang tells search engines that several URLs are the same page in different languages or regions, and which one to show to whom. It is conceptually simple and, in practice, the most error-prone signal in international SEO — because it only works if every page in the cluster agrees with every other.

The cluster has to be symmetrical

If page A lists page B as its Spanish version, page B must list page A as its English version. When the reciprocal reference is missing, the pairing is treated as unconfirmed and ignored. The most common version of this failure is an entirely missing self-reference: a CMS generates the links to sister pages but not the link to the page itself, which invalidates the whole set. This is why checking one page is never enough — you have to check both ends.

Language codes are stricter than they look

The value must be a valid language code, optionally with a region: a two-letter language, an optional script, an optional two-letter country. Underscores instead of hyphens, country-only values, invented region codes and uppercase language codes are all rejected silently. There is no error message anywhere; the tag is simply skipped, and the page it referred to competes as a duplicate instead.

x-default, canonicals and the interaction people get wrong

x-default marks the page to show when no other version matches the user — typically a global landing page or a language picker. It is optional but valuable for international sites. Canonicals are where most clusters break: each language version must canonicalise to itself. Canonicalising every translation to the English original tells search engines the translations should not be indexed at all, which undoes the entire hreflang setup while looking like good housekeeping.

Where to declare it

Hreflang can live in HTML link tags, in HTTP headers, or in the sitemap. All three work. Using more than one at a time is the problem, because the versions drift apart and whichever was parsed most recently wins. Pick one method, implement it everywhere, and re-check after any URL structure change — a migration that redirects one language and not another breaks every cluster it touches.