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 to sitemap for scale)
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. |
Source: hashgraph-online/awesome-codex-plugins → plugins/BestLemoon/codex-seo/skills/seo-hreflang/SKILL.md
1---2name: seo-hreflang-23description: > 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".4---567# Hreflang & International SEO89Validate existing hreflang implementations or generate correct hreflang tags10for multi-language and multi-region sites. Supports HTML, HTTP header, and11XML sitemap implementations.1213## Validation Checks1415### 1. Self-Referencing Tags16- Every page must include an hreflang tag pointing to itself17- The self-referencing URL must exactly match the page's canonical URL18- Missing self-referencing tags cause Google to ignore the entire hreflang set1920### 2. Return Tags21- If page A links to page B with hreflang, page B must link back to page A22- Every hreflang relationship must be bidirectional (A→B and B→A)23- Missing return tags invalidate the hreflang signal for both pages24- Check all language versions reference each other (full mesh)2526### 3. x-default Tag27- Required: designates the fallback page for unmatched languages/regions28- Typically points to the language selector page or English version29- Only one x-default per set of alternates30- Must also have return tags from all other language versions3132### 4. Language Code Validation33- Must use ISO 639-1 two-letter codes (e.g., `en`, `fr`, `de`, `ja`)34- Common errors:35 - `eng` instead of `en` (ISO 639-2, not valid for hreflang)36 - `jp` instead of `ja` (incorrect code for Japanese)37 - `zh` without region qualifier (ambiguous; use `zh-Hans` or `zh-Hant`)3839### 5. Region Code Validation40- Optional region qualifier uses ISO 3166-1 Alpha-2 (e.g., `en-US`, `en-GB`, `pt-BR`)41- Format: `language-REGION` (lowercase language, uppercase region)42- Common errors:43 - `en-uk` instead of `en-GB` (UK is not a valid ISO 3166-1 code)44 - `es-LA` (Latin America is not a country; use specific countries)45 - Region without language prefix4647### 6. Canonical URL Alignment48- Hreflang tags must only appear on canonical URLs49- If a page has `rel=canonical` pointing elsewhere, hreflang on that page is ignored50- The canonical URL and hreflang URL must match exactly (including trailing slashes)51- Non-canonical pages should not be in any hreflang set5253### 7. Protocol Consistency54- All URLs in an hreflang set must use the same protocol (HTTPS or HTTP)55- Mixed HTTP/HTTPS in hreflang sets causes validation failures56- After HTTPS migration, update all hreflang tags to HTTPS5758### 8. Cross-Domain Support59- Hreflang works across different domains (e.g., example.com and example.de)60- Cross-domain hreflang requires return tags on both domains61- Verify both domains are verified in Google Search Console62- Sitemap-based implementation recommended for cross-domain setups6364## Common Mistakes6566| Issue | Severity | Fix |67|-------|----------|-----|68| Missing self-referencing tag | Critical | Add hreflang pointing to same page URL |69| Missing return tags (A→B but no B→A) | Critical | Add matching return tags on all alternates |70| Missing x-default | High | Add x-default pointing to fallback/selector page |71| Invalid language code (e.g., `eng`) | High | Use ISO 639-1 two-letter codes |72| Invalid region code (e.g., `en-uk`) | High | Use ISO 3166-1 Alpha-2 codes |73| Hreflang on non-canonical URL | High | Move hreflang to canonical URL only |74| HTTP/HTTPS mismatch in URLs | Medium | Standardize all URLs to HTTPS |75| Trailing slash inconsistency | Medium | Match canonical URL format exactly |76| Hreflang in both HTML and sitemap | Low | Choose one method (sitemap preferred for large sites) |77| Language without region when needed | Low | Add region qualifier for geo-targeted content |7879## Implementation Methods8081### Method 1: HTML Link Tags82Best for: Sites with <50 language/region variants per page.8384```html85<link rel="alternate" hreflang="en-US" href="https://example.com/page" />86<link rel="alternate" hreflang="en-GB" href="https://example.co.uk/page" />87<link rel="alternate" hreflang="fr" href="https://example.com/fr/page" />88<link rel="alternate" hreflang="x-default" href="https://example.com/page" />89```9091Place in `<head>` section. Every page must include all alternates including itself.9293### Method 2: HTTP Headers94Best for: Non-HTML files (PDFs, documents).9596```97Link: <https://example.com/page>; rel="alternate"; hreflang="en-US",98 <https://example.com/fr/page>; rel="alternate"; hreflang="fr",99 <https://example.com/page>; rel="alternate"; hreflang="x-default"100```101102Set via server configuration or CDN rules.103104### Method 3: XML Sitemap (Recommended for large sites)105Best for: Sites with many language variants, cross-domain setups, or 50+ pages.106107See Hreflang Sitemap Generation section below.108109### Method Comparison110| Method | Best For | Pros | Cons |111|--------|----------|------|------|112| HTML link tags | Small sites (<50 variants) | Easy to implement, visible in source | Bloats `<head>`, hard to maintain at scale |113| HTTP headers | Non-HTML files | Works for PDFs, images | Complex server config, not visible in HTML |114| XML sitemap | Large sites, cross-domain | Scalable, centralized management | Not visible on page, requires sitemap maintenance |115116## Hreflang Generation117118### Process1191. **Detect languages**: Scan site for language indicators (URL path, subdomain, TLD, HTML lang attribute)1202. **Map page equivalents**: Match corresponding pages across languages/regions1213. **Validate language codes**: Verify all codes against ISO 639-1 and ISO 3166-11224. **Generate tags**: Create hreflang tags for each page including self-referencing1235. **Verify return tags**: Confirm all relationships are bidirectional1246. **Add x-default**: Set fallback for each page set1257. **Output**: Generate implementation code (HTML, HTTP headers, or sitemap XML)126127## Hreflang Sitemap Generation128129### Sitemap with Hreflang130```xml131<?xml version="1.0" encoding="UTF-8"?>132<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"133 xmlns:xhtml="http://www.w3.org/1999/xhtml">134 <url>135 <loc>https://example.com/page</loc>136 <xhtml:link rel="alternate" hreflang="en-US" href="https://example.com/page" />137 <xhtml:link rel="alternate" hreflang="fr" href="https://example.com/fr/page" />138 <xhtml:link rel="alternate" hreflang="de" href="https://example.de/page" />139 <xhtml:link rel="alternate" hreflang="x-default" href="https://example.com/page" />140 </url>141 <url>142 <loc>https://example.com/fr/page</loc>143 <xhtml:link rel="alternate" hreflang="en-US" href="https://example.com/page" />144 <xhtml:link rel="alternate" hreflang="fr" href="https://example.com/fr/page" />145 <xhtml:link rel="alternate" hreflang="de" href="https://example.de/page" />146 <xhtml:link rel="alternate" hreflang="x-default" href="https://example.com/page" />147 </url>148</urlset>149```150151Key rules:152- Include the `xmlns:xhtml` namespace declaration153- Every `<url>` entry must include ALL language alternates (including itself)154- Each alternate must appear as a separate `<url>` entry with its own full set155- Split at 50,000 URLs per sitemap file156157## Output158159### Hreflang Validation Report160161#### Summary162- Total pages scanned: XX163- Language variants detected: XX164- Issues found: XX (Critical: X, High: X, Medium: X, Low: X)165166#### Validation Results167| Language | URL | Self-Ref | Return Tags | x-default | Status |168|----------|-----|----------|-------------|-----------|--------|169| en-US | https://... | ✅ | ✅ | ✅ | ✅ |170| fr | https://... | ❌ | ⚠️ | ✅ | ❌ |171| de | https://... | ✅ | ❌ | ✅ | ❌ |172173### Generated Hreflang Tags174- HTML `<link>` tags (if HTML method chosen)175- HTTP header values (if header method chosen)176- `hreflang-sitemap.xml` (if sitemap method chosen)177178### Recommendations179- Missing implementations to add180- Incorrect codes to fix181- Method migration suggestions (e.g., HTML to sitemap for scale)182183## Error Handling184185| Scenario | Action |186|----------|--------|187| URL unreachable (DNS failure, connection refused) | Report the error clearly. Do not guess site structure. Suggest the user verify the URL and try again. |188| No hreflang tags found | Report the absence. Check for other internationalization signals (subdirectories, subdomains, ccTLDs) and recommend the appropriate hreflang implementation method. |189| Invalid language/region codes detected | List each invalid code with the correct replacement. Provide a corrected hreflang tag set ready to implement. |190191---192193**Source:** [`hashgraph-online/awesome-codex-plugins`](https://github.com/hashgraph-online/awesome-codex-plugins) → `plugins/BestLemoon/codex-seo/skills/seo-hreflang/SKILL.md`
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