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=canonicalpointing 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:xhtmlnamespace 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 to sitemap for scale)
Cultural Adaptation Assessment
When analyzing a multi-language site, go beyond technical hreflang validation to assess whether the content is culturally adapted for each target market.
Load references/cultural-profiles.md for pre-built profiles (DACH, Francophone, Hispanic, Japanese).
Assessment steps:
- Identify all language versions and their target markets
- Load the relevant cultural profile(s)
- Check CTAs match cultural expectations (direct vs indirect)
- Check trust signals are locale-appropriate (certifications, legal pages)
- Check for foreign brand references on localized pages
- Check number/date/currency formatting consistency
- Flag cultural adaptation issues as Medium severity
Output: Cultural Adaptation Score per language version (0-100) with specific findings.
Content Parity Audit
Command: /seo hreflang audit <directory-or-url>
Audit content parity across all language versions of a site or local content directory.
Load references/content-parity.md for the full parity matrix and scoring methodology.
What it checks:
- Page existence across all declared languages
- Section structure equivalence (H2/H3 count)
- SEO element parity (title, meta, schema localization)
- Word count ratio validation (DE should be 25-35% longer than EN, JA 10-25% shorter)
- Freshness tracking (stale translations detected via timestamps)
- Cultural marker scanning (foreign brands, wrong legal references, untranslated elements)
Output: Parity matrix table with per-page scores and prioritized action items.
Locale Format Validation
Load references/locale-formats.md for number, date, currency, address, and phone format reference tables per locale.
Checks:
- Number format consistency (e.g., "1,000.00" should be "1.000,00" on de-DE pages)
- Date format matches locale expectations
- Currency symbols and placement correct for target market
- Phone numbers use international format with correct country code
Reference Files
Load on-demand as needed (do NOT load all at startup):
references/cultural-profiles.md: DACH, Francophone, Hispanic, Japanese cultural adaptation profilesreferences/locale-formats.md: Number, date, currency, address, phone format tables per localereferences/content-parity.md: Content parity audit methodology and scoring
Error Handling
| Scenario | Action |
|---|---|
| URL unreachable (DNS failure, connection refused) | Report the error clearly. Do not guess site structure. Suggest the user verify the URL and try again. |
| No hreflang tags found | Report the absence. Check for other internationalization signals (subdirectories, subdomains, ccTLDs) and recommend the appropriate hreflang implementation method. |
| Invalid language/region codes detected | List each invalid code with the correct replacement. Provide a corrected hreflang tag set ready to implement. |
| Cultural profile not available for language | Use the Default Profile checklist from cultural-profiles.md. Note that assessment is based on general guidelines, not a pre-built profile. |
| Content parity directory empty | Report that no content files were found. Suggest verifying the directory path or providing a URL for live site analysis. |