Choose one of three implementation methods: HTTP Link headers, in-page link rel hreflang tags in the HTML head, or sitemap xhtml:link annotations — pick one method and apply it consistently across all versions of every page
For each page variant, include hreflang tags pointing to all language/region variants including the page itself; every page must self-reference its own hreflang value
Always include an x-default hreflang tag pointing to the fallback URL for users whose language/region does not match any defined variant
Validate reciprocity: every URL referenced in a hreflang annotation must itself reference back to the originating URL with a corresponding hreflang; use a crawler or a script to check cross-page consistency
Use BCP 47 language tags (e.g., en-US, pt-BR, zh-Hant) and verify correct region subtag casing (language lowercase, region uppercase)
Known gotchas
Reciprocity errors — where page A points to page B but page B does not return-point to page A — cause Google to ignore the entire hreflang cluster for those pages, silently breaking international targeting
Implementing hreflang in sitemaps is operationally easier to maintain for large sites but requires the sitemap to be regenerated and resubmitted every time new language variants are added
Using the wrong locale code (e.g., zh instead of zh-Hans or zh-Hant) can cause Google to misidentify the target audience; zh alone is not a valid BCP 47 region-language combination for Chinese targeting
Give your agent this knowledge — and 200+ more routes
One MCP install gives any agent live access to the full route map, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp