seo-hreflang

name	seo-hreflang
description	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".
user-invokable	true
argument-hint	[url]
license	MIT
metadata	{"author":"AgriciDaniel","version":"1.9.6","category":"seo"}

Hreflang & International SEO

Shared Data Cache

Step 0 -- Check shared data cache:

Before gathering, check .seo-cache/ for reusable context from related SEO skills. Reference: ../seo/references/shared-data-cache.md for schemas and dependency map.

Check these cache files when present:

• .seo-cache/site-meta.json for domain, business type, industry, and crawl context

• .seo-cache/audit-scores.json for prior full-audit priorities

• .seo-cache/pages/{url-slug}/page-analysis.json for page-level context when a URL is provided

• If found: parse and use clearly valid fields (note "Using cached [X] from [date]")

• If missing, corrupt, or irrelevant: continue with fresh evidence

• If the user says "refresh" or "re-run": ignore cache reads and overwrite on write

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

1. Detect languages: Scan site for language indicators (URL path, subdomain, TLD, HTML lang attribute)
2. Map page equivalents: Match corresponding pages across languages/regions
3. Validate language codes: Verify all codes against ISO 639-1 and ISO 3166-1
4. Generate tags: Create hreflang tags for each page including self-referencing
5. Verify return tags: Confirm all relationships are bidirectional
6. Add x-default: Set fallback for each page set
7. 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 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:

1. Identify all language versions and their target markets
2. Load the relevant cultural profile(s)
3. Check CTAs match cultural expectations (direct vs indirect)
4. Check trust signals are locale-appropriate (certifications, legal pages)
5. Check for foreign brand references on localized pages
6. Check number/date/currency formatting consistency
7. 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 profiles
• references/locale-formats.md: Number, date, currency, address, phone format tables per locale
• references/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.

Write to shared data cache

After completing all work, write a concise JSON summary to .seo-cache/ when the workflow produced durable findings. Use the schemas and naming rules in ../seo/references/shared-data-cache.md; include at least cache_type, analyzed_at, source URL/domain, key findings, issues, recommendations, and tool limitations. Add .seo-cache/ to .gitignore if it is missing.