seo-hreflang

# Hreflang & International SEO Validate existing hreflang implementations or generate correct hreflang tags for multi-language and multi-region sites. Supports HTML, HTTP header, and XML sitemap implementations. ## Validation Checks ### 1. Self-Referencing Tags - Every page must include an hreflang tag pointing to itself - The self-referencing URL must exactly match the page's canonical URL - Missing self-referencing tags cause Google to ignore the entire hreflang set ### 2. Return Tags - If page A links to page B with hreflang, page B must link back to page A - Every hreflang relationship must be bidirectional (A→B and B→A) - Missing return tags invalidate the hreflang signal for both pages - Check all language versions reference each other (full mesh) ### 3. x-default Tag - Recommended when a selector/fallback URL exists: designates the fallback page for unmatched languages/regions - Typically points to the language selector page or English version - Only one x-default per set of alternates - Must also have return tags from all other language versions ### 4. Language Code Validation - Must use ISO 639-1 two-letter codes (e.g., `en`, `fr`, `de`, `ja`) - An **optional ISO 15924 script subtag** is the documented, official mechanism for script: `zh-Hant` (Traditional) / `zh-Hans` (Simplified). Script may combine with a region, e.g. `zh-Hans-US` is valid (language + script + region). - Common errors: - `eng` instead of `en` (ISO 639-2, ...