How to Do SEO for a Bilingual Website: Language Versions, URLs, and Markup Configuration

To avoid confusion between language versions, a bilingual website should first give each language its own crawlable URL. Then use hreflang to declare the relationship between versions, and ensure that canonical URLs match the actual pages. Language switching, redirects, and sitemaps should all follow the same URL rules. Translating pages or adding language annotations alone cannot solve version identification issues.

First, define the relationship between languages and regions

When planning bilingual SEO, first distinguish between language versions and regional versions. Chinese and English pages can use zh and en, respectively. If the English pages also provide different prices, shipping, or contact details for the US and the UK, you can use en-US and en-GB. Region codes should reflect real regional differences. Avoid duplicating large numbers of identical pages solely to cover more search terms.

The language and region codes must not be reversed: en-US represents an English-language page targeting the US, while US alone cannot be used as a language value. Script subtags can also distinguish Simplified and Traditional Chinese, for example, zh-Hans and zh-Hant. Before publishing, decide whether pages are differentiated by language, writing system, or region to avoid cascading URL and markup changes later.

Search engines use visible page content to identify its language. Do not translate only the navigation and footer while leaving the main content in another language. Product names and industry terms do not need to be forcibly translated, but titles, body copy, and key action information should match the language of that version.

URL structure determines future maintenance costs

Common structures for bilingual pages include subdirectories on the same domain, different subdomains, and different country- or region-specific domains. For example, example.com/zh/ and example.com/en/ use subdirectories, while zh.example.com and en.example.com use subdomains. All three structures can host multilingual pages. When choosing one, focus on deployment, permissions, and long-term maintenance.

Subdirectories make it easier to manage language paths within the same site. Subdomains are suitable when separate deployment or permission isolation is needed. Different domains can be managed separately for branding and site operations, but each requires its own DNS configuration, renewals, certificates, and cross-domain annotations. Domains with country- or region-specific meanings also send a clear regional signal, so do not use them for unrelated markets merely because the extension is available for registration.

When planning different domains, clarify domain ownership and DNS responsibilities before launch. Domain services cover domain searches, registration, DNS configuration, and renewal reminders. If each language site uses a different domain, these items need to be checked separately, and automatic DNS configuration should be verified against the records that ultimately take effect.

Each language page should have a stable, directly accessible URL, such as /en/products/pump/ and /zh/products/pump/. Do not use the same URL to return completely different body content based only on the browser language; this makes it difficult for crawlers and indexers to reliably associate each language version with its URL. Query parameters can distinguish pages, but require additional controls for parameter combinations, canonical URLs, and internal links to avoid generating unnecessary duplicate URLs.

Ensure hreflang annotations cover all corresponding pages

hreflang expresses the relationship between pages in different languages or regions. It is a signal that helps search engines choose which version to display, but does not guarantee that a specific page will be indexed or shown. Annotations can be placed in the HTML head, HTTP response headers, or an XML sitemap. Keep the configuration consistent across each set of pages to avoid conflicting relationships in different locations.

In the example below, the Chinese and English product pages are alternate versions of each other, and each page declares itself. Both pages use the same annotations, with full URLs:

<link rel="alternate" hreflang="zh"
      href="https://example.com/zh/products/pump/">
<link rel="alternate" hreflang="en"
      href="https://example.com/en/products/pump/">
<link rel="alternate" hreflang="x-default"
      href="https://example.com/language-selector/">

x-default is a fallback for cases where no other language or regional version matches. It can point to a language selector or a page suitable for default visitors. It is optional and is not the same as the English version. If the fallback URL is included in this set of relationships, that page should also output the same corresponding annotations.

Establish relationships between pages with equivalent content: a Chinese product detail page should correspond to its English product detail page, not always point to the English homepage. If an article has not been translated, do not mark it as an alternate version of the homepage in another language. The URLs in the annotations should resolve to accessible final pages, not redirects, error pages, or URLs blocked from indexing.

How canonical URLs work with language switching

canonical and hreflang address different issues. The former declares the URL preferred as the canonical version, while the latter describes alternate language or regional versions. When Chinese and English pages each contain complete content, they would typically each point to their own canonical URL and declare hreflang annotations for one another. If the English page's canonical URL points to the Chinese page, this may reduce the likelihood of the English page being indexed as an independent version.

For URLs with tracking parameters, sorting parameters, or similar parameters in the same language, determine whether they should be consolidated under a canonical URL based on the page content. Do not treat two pages as duplicates simply because they belong to the same set of language versions. Sitemaps and internal links should also prioritize canonical URLs to reduce conflicting signals.

Language-switching links should point directly to the translated equivalent of the current content whenever possible, using ordinary crawlable links. If no translation is available, you can direct users to a relevant section in that language, but do not present this redirect relationship as an equivalent hreflang relationship. Automatic redirects based on browser language or geographic location may also prevent crawlers from accessing other versions. Keeping a clear switching option and allowing direct access to URLs in each language makes verification easier.

How to identify configuration issues after launch

Start with a set of pages that actually correspond to one another, and check the final response status, visible page language, canonical URL, and complete hreflang set for each. The Chinese and English pages should point to each other. If only the Chinese page declares the English page, with no reciprocal relationship from the English page, search engines may ignore the annotations. When generating annotations in bulk, be especially sure that pages whose translations have not yet launched are not incorrectly included.

Crawl testing should also distinguish between the original HTML returned by the server and the content after browser scripts have run. If language links or annotations are generated by scripts, confirm that they are visible after rendering and do not conflict with the original markup. For non-HTML files such as PDFs, you can consider declaring alternate language relationships through HTTP response headers. Blocking crawlers in robots.txt can prevent search engines from reading annotations on a page, while noindex conflicts with the goal of having that page indexed.

If search results show the wrong language, first check the search query, search region, and actual landing page, then investigate annotations, canonicalization, and redirects. A search result appearing in another language does not necessarily indicate a configuration error. If the page itself mixes languages or the two pages do not correspond in content, changing hreflang alone cannot correct the content relationship.