fix(seo): normalize locale codes to BCP 47 for lang and hreflang attributes#18246
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…ibutes Locale codes pt-br and zh-tw are used as URL path segments (intentional) but were also used directly as HTML lang attributes and hreflang language keys, which require uppercase region subtags per BCP 47 (pt-BR, zh-TW). Adds toLanguageTag() utility and applies it in: - app/[locale]/layout.tsx: <html lang> - src/lib/utils/metadata.ts: hreflang language keys - app/sitemap.ts: sitemap hreflang alternates Fixes ~142 "HTML lang attribute invalid" ahrefs errors.
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@wackerow AI found this, not sure it's valid, not a rush, but whenever can you check? |
wackerow
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May 28, 2026
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Looks good! Checks/test look clean. Thanks!
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Summary
toLanguageTag()utility insrc/lib/utils/url.tsthat converts internal locale codes to valid BCP 47 language tags (pt-br→pt-BR,zh-tw→zh-TW)<html lang>attribute inapp/[locale]/layout.tsxsrc/lib/utils/metadata.tsandapp/sitemap.tsContext
Identified via ahrefs weekly crawl (20 May 2026): 142 "HTML lang attribute invalid" errors.
Internal locale codes use lowercase region subtags (e.g.
pt-br,zh-tw) as URL path segments — that is intentional and unchanged. But the same raw codes were being used as HTMLlangattributes and hreflang language keys, which require BCP 47 format with uppercase region subtags (pt-BR,zh-TW). All other locales (single-segment likeen,fr,ar) are unaffected.Test plan
<html lang="pt-BR">and<html lang="zh-TW">are rendered on those locale pages<head>usept-BR/zh-TWas language keys/pt-br/,/zh-tw/) are unchanged