Hreflang.

Hreflang annotations link pages that are equivalent in content across different languages or countries. With rel=«alternate» hreflang=«de-CH» a page signals: this is the version for German-speaking users in Switzerland. Google can then serve the appropriate variant to each user out of several. The annotation says nothing about quality and gives no ranking boost. It is purely a routing instruction that decides which of your existing versions is shown to whom, which is why it can only ever help a site that genuinely has more than one version.

The value combines a language code (ISO 639-1, for example de, fr, it) optionally with a country code (ISO 3166-1, for example CH, DE, AT). For Switzerland the relevant ones are de-CH, fr-CH and it-CH, covering the national languages, while en-CH is common for pages aimed at international companies and expats based in the country. In addition, x-default points to a fallback version for every case not otherwise covered. Language codes come first and stand alone; a country code without a language code is invalid.

Reciprocity is decisive. If page A points to page B via hreflang, B must point back to A. Where that return reference is missing, or the language codes are wrong, Google ignores the annotations altogether rather than guessing. Another frequent mistake is mixing language and country variants without a clean system, for instance listing de, de-CH and de-DE side by side with no rule for who receives which. Every version in the set must also list itself, which is the step most often forgotten.

An example. A Swiss service provider with a German and a French site places one hreflang block on each, pointing to both language versions plus x-default. A user in Geneva then lands on the French page and one in Zurich on the German page, without the two being treated as duplicate content. The same applies to a German-English pair: the English page names the German one and the German page names the English one. Without that mutual reference Google treats the pairing as unconfirmed and quietly disregards it.