Skill

seo-hreflang

Hreflang and international SEO audit, validation, and generation. Detects common mistakes, validates language/region codes, and generates correct hreflang implementations. Use when user says "hreflang", "i18n SEO", "international SEO", "multi-language", "multi-region", or "language tags".

From muggle-ai-teams

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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

Required: 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)
Common errors:
- eng instead of en (ISO 639-2, not valid for hreflang)
- jp instead of ja (incorrect code for Japanese)
- zh without region qualifier (ambiguous — use zh-Hans or zh-Hant)

5. Region Code Validation

Optional region qualifier uses ISO 3166-1 Alpha-2 (e.g., en-US, en-GB, pt-BR)
Format: language-REGION (lowercase language, uppercase region)
Common errors:
- en-uk instead of en-GB (UK is not a valid ISO 3166-1 code)
- es-LA (Latin America is not a country — use specific countries)
- Region without language prefix

6. Canonical URL Alignment

Hreflang tags must only appear on canonical URLs
If a page has rel=canonical pointing elsewhere, hreflang on that page is ignored
The canonical URL and hreflang URL must match exactly (including trailing slashes)
Non-canonical pages should not be in any hreflang set

7. Protocol Consistency

All URLs in an hreflang set must use the same protocol (HTTPS or HTTP)
Mixed HTTP/HTTPS in hreflang sets causes validation failures
After HTTPS migration, update all hreflang tags to HTTPS

8. Cross-Domain Support

Hreflang works across different domains (e.g., example.com and example.de)
Cross-domain hreflang requires return tags on both domains
Verify both domains are verified in Google Search Console
Sitemap-based implementation recommended for cross-domain setups

Common Mistakes

Issue	Severity	Fix
Missing self-referencing tag	Critical	Add hreflang pointing to same page URL
Missing return tags (A→B but no B→A)	Critical	Add matching return tags on all alternates
Missing x-default	High	Add x-default pointing to fallback/selector page
Invalid language code (e.g., `eng`)	High	Use ISO 639-1 two-letter codes
Invalid region code (e.g., `en-uk`)	High	Use ISO 3166-1 Alpha-2 codes
Hreflang on non-canonical URL	High	Move hreflang to canonical URL only
HTTP/HTTPS mismatch in URLs	Medium	Standardize all URLs to HTTPS
Trailing slash inconsistency	Medium	Match canonical URL format exactly
Hreflang in both HTML and sitemap	Low	Choose one method — sitemap preferred for large sites
Language without region when needed	Low	Add region qualifier for geo-targeted content

Implementation Methods

Method 1: HTML Link Tags

Best for: Sites with <50 language/region variants per page.

<link rel="alternate" hreflang="en-US" href="https://example.com/page" />
<link rel="alternate" hreflang="en-GB" href="https://example.co.uk/page" />
<link rel="alternate" hreflang="fr" href="https://example.com/fr/page" />
<link rel="alternate" hreflang="x-default" href="https://example.com/page" />

Place in <head> section. Every page must include all alternates including itself.

Method 2: HTTP Headers

Best for: Non-HTML files (PDFs, documents).

Link: <https://example.com/page>; rel="alternate"; hreflang="en-US",
      <https://example.com/fr/page>; rel="alternate"; hreflang="fr",
      <https://example.com/page>; rel="alternate"; hreflang="x-default"

Set via server configuration or CDN rules.

Method 3: XML Sitemap (Recommended for large sites)

Best for: Sites with many language variants, cross-domain setups, or 50+ pages.

See Hreflang Sitemap Generation section below.

Method Comparison

Method	Best For	Pros	Cons
HTML link tags	Small sites (<50 variants)	Easy to implement, visible in source	Bloats `<head>`, hard to maintain at scale
HTTP headers	Non-HTML files	Works for PDFs, images	Complex server config, not visible in HTML
XML sitemap	Large sites, cross-domain	Scalable, centralized management	Not visible on page, requires sitemap maintenance

Hreflang Generation

Process

Detect languages: Scan site for language indicators (URL path, subdomain, TLD, HTML lang attribute)
Map page equivalents: Match corresponding pages across languages/regions
Validate language codes: Verify all codes against ISO 639-1 and ISO 3166-1
Generate tags: Create hreflang tags for each page including self-referencing
Verify return tags: Confirm all relationships are bidirectional
Add x-default: Set fallback for each page set
Output: Generate implementation code (HTML, HTTP headers, or sitemap XML)

Hreflang Sitemap Generation

Sitemap with Hreflang

<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
        xmlns:xhtml="http://www.w3.org/1999/xhtml">
  <url>
    <loc>https://example.com/page</loc>
    <xhtml:link rel="alternate" hreflang="en-US" href="https://example.com/page" />
    <xhtml:link rel="alternate" hreflang="fr" href="https://example.com/fr/page" />
    <xhtml:link rel="alternate" hreflang="de" href="https://example.de/page" />
    <xhtml:link rel="alternate" hreflang="x-default" href="https://example.com/page" />
  </url>
  <url>
    <loc>https://example.com/fr/page</loc>
    <xhtml:link rel="alternate" hreflang="en-US" href="https://example.com/page" />
    <xhtml:link rel="alternate" hreflang="fr" href="https://example.com/fr/page" />
    <xhtml:link rel="alternate" hreflang="de" href="https://example.de/page" />
    <xhtml:link rel="alternate" hreflang="x-default" href="https://example.com/page" />
  </url>
</urlset>

Key rules:

Include the xmlns:xhtml namespace declaration
Every <url> entry must include ALL language alternates (including itself)
Each alternate must appear as a separate <url> entry with its own full set
Split at 50,000 URLs per sitemap file

Output

Hreflang Validation Report

Summary

Total pages scanned: XX
Language variants detected: XX
Issues found: XX (Critical: X, High: X, Medium: X, Low: X)

Validation Results

Language	URL	Self-Ref	Return Tags	x-default	Status
en-US	https://...	✅	✅	✅	✅
fr	https://...	❌	⚠️	✅	❌
de	https://...	✅	❌	✅	❌

Generated Hreflang Tags

HTML <link> tags (if HTML method chosen)
HTTP header values (if header method chosen)
hreflang-sitemap.xml (if sitemap method chosen)

Recommendations

Missing implementations to add
Incorrect codes to fix
Method migration suggestions (e.g., HTML → sitemap for scale)