Definition
hreflang is an HTML link attribute (or sitemap annotation) that tells search engines which language and regional version of a page to show to users in different locales. The tag uses the format <link rel="alternate" hreflang="en" href="..." /> and must be reciprocal: if the English page points to the Chinese version, the Chinese page must point back. For GEO, hreflang matters because AI engines that retrieve results from Google or Bing inherit the language-matching logic: a query in Chinese should retrieve your /zh/ page, not the English version. Incorrect hreflang (missing reciprocal tags, wrong language codes, broken URLs) can cause the wrong language variant to appear in AI answers — or cause both variants to compete and dilute each other's authority. Common mistakes include using country codes ("cn") instead of language codes ("zh"), omitting the x-default fallback, and failing to update hreflang when adding new language variants. For bilingual GEO sites, audit hreflang with Google Search Console's international targeting report and validate that AI engines return the correct language variant for locale-specific prompts.