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fix(seo): normalize locale codes to BCP 47 for lang and hreflang attributes #18246

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Merged
wackerow merged 1 commit into from
May 28, 2026
Merged

fix(seo): normalize locale codes to BCP 47 for lang and hreflang attributes #18246

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3 changes: 2 additions & 1 deletion app/[locale]/layout.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ import Matomo from "@/components/Matomo"

import { getLastDeployDate } from "@/lib/utils/getLastDeployDate"
import { getLocaleTimestamp } from "@/lib/utils/time"
import { toLanguageTag } from "@/lib/utils/url"

import Providers from "./providers"

Expand Down Expand Up @@ -66,7 +67,7 @@ export default async function LocaleLayout(props: {

return (
<html
lang={locale}
lang={toLanguageTag(locale)}
className={`${inter.variable} ${ibmPlexMono.variable}`}
suppressHydrationWarning
>
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4 changes: 2 additions & 2 deletions app/sitemap.ts
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@@ -1,6 +1,6 @@
import type { MetadataRoute } from "next"

import { getFullUrl } from "@/lib/utils/url"
import { getFullUrl, toLanguageTag } from "@/lib/utils/url"

import { DEFAULT_LOCALE } from "@/lib/constants"

Expand All @@ -21,7 +21,7 @@ export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
"x-default": getFullUrl(DEFAULT_LOCALE, normalizedSlug),
...Object.fromEntries(
translatedLocales.map((locale) => [
locale,
toLanguageTag(locale),
getFullUrl(locale, normalizedSlug),
])
),
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7 changes: 5 additions & 2 deletions src/lib/utils/metadata.ts
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Expand Up @@ -9,7 +9,7 @@ import {

import { getTranslatedLocales } from "../i18n/translationRegistry"

import { getFullUrl } from "./url"
import { getFullUrl, toLanguageTag } from "./url"

import { routing } from "@/i18n/routing"

Expand Down Expand Up @@ -103,7 +103,10 @@ export const getMetadata = async ({
languages: {
"x-default": xDefault,
...Object.fromEntries(
localesForHreflang.map((loc) => [loc, getFullUrl(loc, slugString)])
localesForHreflang.map((loc) => [
toLanguageTag(loc),
getFullUrl(loc, slugString),
])
),
},
}),
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12 changes: 12 additions & 0 deletions src/lib/utils/url.ts
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Expand Up @@ -115,6 +115,18 @@ export const slugify = (text: string): string => {
)
}

/**
* Converts an internal locale code to a valid BCP 47 language tag.
* Internal codes use lowercase region subtags (e.g. "pt-br", "zh-tw")
* for use as URL path segments, but HTML lang and hreflang attributes
* require uppercase region subtags per BCP 47 (e.g. "pt-BR", "zh-TW").
*/
export const toLanguageTag = (locale: string): string => {
const parts = locale.split("-")
if (parts.length === 2) return `${parts[0]}-${parts[1].toUpperCase()}`
return locale
}

export const normalizeUrlForJsonLd = (
locale: string | Lang | undefined,
pathWithoutLocale: string
Expand Down
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