Real Bilingual Blog Refactor: Routes, hreflang, and Consistent SEO

Building a bilingual blog is not just translation work. If route architecture, canonical strategy, and navigation are not aligned, you get duplicate content, indexing confusion, and users landing in mixed-language sections.

This refactor solved that from end to end. Here is the practical walkthrough.

Initial Problem

We had clear symptoms:

• /blog was mixing Spanish and English posts,
• old non-localized URLs were still active,
• direct URL visitors did not get consistent language behavior,
• Search Console showed canonical conflicts and duplicates.

Goal: language-consistent UX and crawl-friendly SEO.

Architecture Decisions

We standardized around five rules:

1. Language-first routes: /{lang}/...
2. Smart redirects for generic routes (/, /blog, /tags)
3. Per-post hreflang + x-default
4. Language preference cookie (site_lang)
5. Localized pages for home, tags, and category hubs

Step 1: Localized Pages

We implemented language-aware pages:

• src/pages/[lang]/index.astro
• src/pages/[lang]/blog/[...slug].astro
• src/pages/[lang]/blog/index.astro
• src/pages/[lang]/blog/category/index.astro
• src/pages/[lang]/tags/index.astro
• src/pages/[lang]/tags/[tag].astro

This removes ambiguity and makes language explicit in every route.

Step 2: Middleware Redirect Strategy

Middleware now resolves language from cookie + Accept-Language, then redirects generic routes.

Simplified logic:

const preferredLang = cookieLang ?? detectLangFromHeader(acceptLanguageHeader);

if (normalizedPath === "/") {
  return Response.redirect(new URL(`/${preferredLang}/`, url.origin), 302);
}

if (normalizedPath === "/blog") {
  return Response.redirect(new URL(`/${preferredLang}/blog/`, url.origin), 302);
}

Result: no more mixed-language listing pages.

Step 3: Canonical and hreflang

We extended SEO metadata to include language alternates:

export interface LanguageAlternateEntry {
  lang: string;
  url: string;
}

Per post, alternates are computed by translationKey and include x-default.

const alternates = translations.map((translation) => ({
  lang: translation.data.lang,
  url: `${siteUrl}${translation.data.lang}/blog/${translation.id}/`,
}));
alternates.push({ lang: "x-default", url: `${siteUrl}en/blog/${defaultId}/` });

This gives search engines explicit language mapping and reduces canonical ambiguity.

Step 4: Navigation Consistency

The header was updated to preserve language context:

• Home -> /${lang}
• Tags -> /${lang}/tags
• Categories -> /${lang}/blog/category

We also added an explicit ES | EN switcher and persist user choice via cookie.

Step 5: Remove Duplicate “Related” UX

Some migrated posts had both:

• markdown “Related” link list,
• visual related-posts component.

That created duplicated sections and visual noise. We removed markdown duplicates and kept the component-based related cards.

Step 6: Translation Coverage Report

To prevent ES/EN drift, we added a coverage report:

pnpm run seo:report-translations

Output:

• docs/seo/translation-coverage.md

This catches incomplete translation keys before release.

Step 7: QA Checklist After Refactor

• /blog redirects to /{lang}/blog/
• /tags redirects to /{lang}/tags/
• post canonical matches localized URL
• hreflang includes ES/EN + x-default
• no mixed-language listing pages
• build passes cleanly

Common Mistakes in Bilingual Refactors

1. Translating content but keeping non-localized URLs.
2. Localized routes without metadata parity.
3. Navigation that breaks language context.
4. Redirect chains without a clear policy.
5. No automated translation coverage audit.

Publishing Opportunities From This Refactor

This refactor itself can become a technical series:

1. Language route architecture in Astro.
2. Practical international SEO: canonical + hreflang.
3. Migration strategy that preserves indexing stability.

Close

The biggest win was not “having two languages.” The real win was consistency across user navigation, metadata, and crawl behavior.

If you are planning a similar migration, do not start with translation copywriting. Start with route architecture, canonical strategy, and redirect behavior.

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