🌍 Multilingual Website SEO (AEO, GEO) Best Practices: Subdirectory Structure & Language Code Standards
In today’s globalized web environment, supporting multilingual websites has become standard for many brands.
However, achieving strong SEO performance across different languages is a key area that many developers and operators often overlook.
This article will systematically cover:
- Why using subdirectory (subfolder) structures is the SEO-optimal choice;
- How to correctly set language paths like
/en/and/zh-Hans/; - Where to find standard language codes (e.g.,
esfor Spanish).
1. Why Choose a Subdirectory Structure?
In multilingual SEO, URL structure is one of the most important signals for search engines to understand the language version of a site.
Common approaches include:
- Different top-level domains (ccTLDs): e.g.,
example.cn,example.fr - Subdomains: e.g.,
zh.example.com - Subdirectories (subfolders): e.g.,
example.com/zh-Hans/ - URL parameters: e.g.,
example.com/?lang=zh
Google’s official recommendation:
“Use different URLs to serve content for different language versions.”
— Managing Multi-Regional and Multilingual Sites
Among these options, subdirectory/subfolder structures are the most balanced and cost-effective solution because they offer the following advantages:
| Advantage | Explanation |
|---|---|
| 🔗 Inherits main domain authority | All language versions share the main domain, helping to consolidate SEO authority. |
| ⚙️ Easy to maintain | No need to manage multiple domains or additional SSL/multi-site configurations. |
| 🧭 Clear structure | /en/, /zh-Hans/ make it obvious for both search engines and users. |
| 📈 Analytics-friendly | You can compare the performance of different language folders within the same analytics property. |
URL parameter-based structures (e.g., ?lang=en) are generally not recommended, as they negatively impact indexing, readability, and link equity.2. Recommended URL Structure Examples
Assume your main domain is example.com. Recommended multilingual structure:
| Language | Example URL | Recommendation |
|---|---|---|
| English | https://www.example.com/en/ | Generic English version |
| Simplified Chinese | https://www.example.com/zh-Hans/ | Explicitly marked as Simplified Chinese (Hans = simplified script) |
Notes:
- Use
zh-Hansinstead of justzhorzh-CN, as Google’s hreflang supports script codes. - For Traditional Chinese, use
zh-Hant. - Each language version should have fully translated content, including page titles, meta tags, navigation, and slugs.
Example:
/en/how-to-use-product//zh-Hans/如何使用产品/
3. SEO Elements You Must Configure
1️⃣ Hreflang Tags
Tell search engines the language version of each page.
<link rel="alternate" hreflang="en" href="https://www.example.com/en/page/" /><link rel="alternate" hreflang="zh-Hans" href="https://www.example.com/zh-Hans/page/" /><link rel="alternate" hreflang="x-default" href="https://www.example.com/en/page/" />
Key points:
- Each version should reference each other (bidirectional tagging).
x-defaultis for users with undefined language preferences.- Use BCP 47 language code standards.
2️⃣ HTML lang Attribute
Declare the language in each page’s HTML tag:
<html lang="zh-Hans">
3️⃣ Avoid Automatic Redirects
Do not redirect users based on IP or browser language, as Google cannot access all language versions.
4️⃣ Submit Sitemaps with Language Versions
Include hreflang mappings in your sitemap via Google Search Console to improve indexing accuracy.
4. Standard Sources for Language Codes
A common question in multilingual website development: “What’s the correct language code?”
For example, should Spanish be es or eps? (Correct: es)
| Standard | Description | Example |
|---|---|---|
| ISO 639-1 | Two-letter language codes | en (English), es (Spanish), zh (Chinese) |
| ISO 3166-1 Alpha-2 | Country/region codes | US (United States), CN (China), ES (Spain) |
| BCP 47 | Language + Script + Region combination standard | zh-Hans (Simplified Chinese), zh-Hant (Traditional Chinese), es-MX (Mexican Spanish) |
Authoritative sources for language codes:
- W3C official documentation: Language tags in HTML and XML
- ISO 639-1 list (Wikipedia)
- Google’s guide: Localized versions of your pages
5. Common Pitfalls & How to Avoid Them
| ⚠️ Problem | Why it’s bad |
|---|---|
| Automatic redirects based on IP or language | Search engines cannot access other language versions |
| Using URL parameters to differentiate language | Poor indexing, URLs hard to share |
| Incomplete hreflang tags | Search results may display wrong language versions |
| Partially translated content | Main language detection can fail, affecting rankings |
| Inconsistent URL structure | Confuses users and search engines about language relationships |
6. Summary: Multilingual SEO Golden Rules
- One unique URL per language
Use clear subdirectory paths (/en/,/zh-Hans/). - Correct use of hreflang and
langattributes
Helps search engines understand language relationships. - Consistent content and structure
Align structure and content depth across languages. - Avoid automatic redirects
Allow free access to each language version for users and search engines. - Follow BCP 47 standard codes
Ensure language tags (e.g.,zh-Hans,es-MX) comply with international standards.
📎 Further Reading
- Google Search Central: Managing Multi-Regional and Multilingual Sites
- W3C: Language Tags Reference (BCP 47)
- ISO 639-1 Codes (Wikipedia)
- Contentful Blog: Multilingual SEO Best Practices
🧭 Conclusion
If you plan for your website to truly “speak multiple languages,” the correct URL structure and language tagging is the first step in SEO.
By choosing subdirectory structures, following standardized language codes, and implementing complete hreflang setups, your site can be clearly visible and perform strongly in global search results.
