How to Optimize SEO for a Multilingual Next.js App

February 17, 2026

General Translation

guideseointernationalizationnextjsi18nroutingmetadata

Why multilingual SEO needs special attention

Most developers who add i18n to their Next.js app focus on translating the UI and call it done. But if search engines can't find, index, and properly associate your language versions, all that translation work is invisible.

A multilingual site without proper SEO setup has problems:

Google may index only one language version and ignore the rest
Users searching in Spanish get served the English page
Duplicate content penalties because Google sees /en/about and /fr/about as the same page
Incorrect language shown in search result snippets

The good news: getting multilingual SEO right in Next.js isn't complicated. There are five things you need to get right, and this guide covers all of them using gt-next.

1. Locale-based URL routing

The foundation of multilingual SEO is having distinct URLs for each language. Search engines need separate, crawlable URLs to index each language version independently.

This means locale-in-the-URL — not cookies, not query parameters, not Accept-Language detection alone.

✅ generaltranslation.com/en/about
✅ generaltranslation.com/fr/about
✅ generaltranslation.com/es/about

❌ generaltranslation.com/about?lang=fr
❌ generaltranslation.com/about (with locale in a cookie)

Setting up locale routing with gt-next

First, nest your pages under a [locale] dynamic segment:

app/
└── [locale]/
    ├── layout.tsx
    ├── page.tsx
    └── about/
        └── page.tsx

Then create middleware in your project root (proxy.ts for Next.js 16+, or middleware.ts for Next.js 15 and below):

import { createNextMiddleware } from 'gt-next/middleware';

export default createNextMiddleware();

export const config = {
  matcher: ['/((?!api|static|.*\\..*|_next).*)'],
};

This gives you locale-prefixed URLs automatically. By default, the default locale (e.g., English) doesn't get a prefix — /about stays clean, while Spanish users see /es/about and French users see /fr/about.

2. Setting the HTML `lang` attribute

The lang attribute on your <html> tag tells browsers and search engines which language the page is in. It's one of the simplest and most impactful things you can do for accessibility and SEO.

Without it, screen readers guess the language (often wrong), and search engines have less confidence in their language classification.

gt-next provides the useLocale hook that makes this trivial in your root layout:

import { useLocale, GTProvider } from 'gt-next';

export default function RootLayout({ children }: { children: React.ReactNode }) {
  const locale = useLocale();

  return (
    <html lang={locale}>
      <body>
        <GTProvider>
          {children}
        </GTProvider>
      </body>
    </html>
  );
}

useLocale returns the BCP 47 locale code (e.g., en-US, ar, zh-Hans).

3. Canonical URLs

Canonical tags tell search engines which URL is the "primary" version of a page. For multilingual sites, each language version should point to itself as the canonical:

<!-- On /fr/about -->
<link rel="canonical" href="https://example.com/fr/about" />

This prevents search engines from treating your French page as a duplicate of your English page.

In Next.js, you set canonicals through the metadata API. Combine it with gt-next's getLocale to generate the correct canonical for each locale:

import { getLocale } from 'gt-next/server';

const BASE_URL = 'https://example.com';

export async function generateMetadata() {
  const locale = await getLocale();

  return {
    alternates: {
      canonical: `${BASE_URL}/${locale}/about`,
    },
  };
}

export default function AboutPage() {
  return <h1>About Us</h1>;
}

For the default locale without a prefix, adjust accordingly:

import { getLocale, getDefaultLocale } from 'gt-next/server';

export async function generateMetadata() {
  const locale = await getLocale();
  const defaultLocale = getDefaultLocale();
  const path = '/about';

  const prefix = locale === defaultLocale ? '' : `/${locale}`;

  return {
    alternates: {
      canonical: `${BASE_URL}${prefix}${path}`,
    },
  };
}

4. Hreflang tags

Hreflang tags are the most important multilingual SEO signal. They tell search engines: "this page exists in these other languages, and here are the URLs."

Without hreflang, Google has to guess which language version to show in search results — and it often gets it wrong.

<link rel="alternate" hreflang="en" href="https://example.com/about" />
<link rel="alternate" hreflang="fr" href="https://example.com/fr/about" />
<link rel="alternate" hreflang="es" href="https://example.com/es/about" />
<link rel="alternate" hreflang="x-default" href="https://example.com/about" />

The x-default tag tells search engines which URL to show when none of the specified languages match the user.

In Next.js, you can add hreflang through the metadata API's alternates.languages property. Here's a reusable helper that works with gt-next:

import { getLocale, getDefaultLocale } from 'gt-next/server';

const BASE_URL = 'https://example.com';
const SUPPORTED_LOCALES = ['en', 'fr', 'es'];

export async function getI18NMetadata(path: string) {
  const locale = await getLocale();
  const defaultLocale = getDefaultLocale();

  const getUrl = (loc: string) => {
    const prefix = loc === defaultLocale ? '' : `/${loc}`;
    return `${BASE_URL}${prefix}${path}`;
  };

  const languages: Record<string, string> = {};
  for (const loc of SUPPORTED_LOCALES) {
    languages[loc] = getUrl(loc);
  }
  languages['x-default'] = getUrl(defaultLocale);

  return {
    alternates: {
      canonical: getUrl(locale),
      languages,
    },
  };
}

Then use it in any page:

import { getI18NMetadata } from '@/lib/i18n-metadata';

export async function generateMetadata() {
  return await getI18NMetadata('/about');
}

This generates both the canonical and all hreflang tags in one call.

5. Translated metadata

Search engines display your page title and description in results. If these are in English for a French page, users are less likely to click — and Google may demote the result.

Use gt-next's getGT function to translate metadata strings:

import { getGT } from 'gt-next/server';
import { getI18NMetadata } from '@/lib/i18n-metadata';

export async function generateMetadata() {
  const t = await getGT();
  const i18nMeta = await getI18NMetadata('/about');

  return {
    title: t('About Us'),
    description: t('Learn about our mission and team.'),
    ...i18nMeta,
  };
}

This gives you localized titles and descriptions in search results, which significantly improves click-through rates for non-English queries.

6. Multilingual sitemaps

A sitemap helps search engines discover all your pages, including every language version. For multilingual sites, you should include hreflang annotations in your sitemap as well.

Next.js supports programmatic sitemaps through a sitemap.ts file:

import { MetadataRoute } from 'next';

const BASE_URL = 'https://example.com';
const LOCALES = ['en', 'fr', 'es'];
const DEFAULT_LOCALE = 'en';
const PAGES = ['/', '/about', '/blog', '/contact'];

export default function sitemap(): MetadataRoute.Sitemap {
  return PAGES.flatMap((path) => {
    const getUrl = (locale: string) => {
      const prefix = locale === DEFAULT_LOCALE ? '' : `/${locale}`;
      return `${BASE_URL}${prefix}${path === '/' ? '' : path}`;
    };

    const languages: Record<string, string> = {};
    for (const locale of LOCALES) {
      languages[locale] = getUrl(locale);
    }

    return LOCALES.map((locale) => ({
      url: getUrl(locale),
      lastModified: new Date(),
      alternates: { languages },
    }));
  });
}

This generates a sitemap with one entry per page per locale, and each entry includes hreflang annotations pointing to all language versions.

Checklist

Here's a quick summary of everything covered:

SEO requirement	Implementation
Locale in URL	`createNextMiddleware()` with `[locale]` dynamic segment
HTML `lang` attribute	`useLocale()` in root layout
Canonical URLs	`getLocale()` + Next.js metadata API `alternates.canonical`
Hreflang tags	Next.js metadata API `alternates.languages` with all supported locales
Translated metadata	`getGT()` for page titles and descriptions
Multilingual sitemap	`sitemap.ts` with per-locale entries and hreflang alternates

Next steps

gt-next quickstart to set up the full i18n stack
Middleware guide for routing configuration
SSG guide for statically generating multilingual pages
RTL support for right-to-left languages

Back

How to Optimize SEO for a Multilingual Next.js App

February 17, 2026

General Translation

guideseointernationalizationnextjsi18nroutingmetadata

Why multilingual SEO needs special attention

A multilingual site without proper SEO setup has problems:

Google may index only one language version and ignore the rest
Users searching in Spanish get served the English page
Duplicate content penalties because Google sees /en/about and /fr/about as the same page
Incorrect language shown in search result snippets

The good news: getting multilingual SEO right in Next.js isn't complicated. There are five things you need to get right, and this guide covers all of them using gt-next.

1. Locale-based URL routing

The foundation of multilingual SEO is having distinct URLs for each language. Search engines need separate, crawlable URLs to index each language version independently.

This means locale-in-the-URL — not cookies, not query parameters, not Accept-Language detection alone.

✅ generaltranslation.com/en/about
✅ generaltranslation.com/fr/about
✅ generaltranslation.com/es/about

❌ generaltranslation.com/about?lang=fr
❌ generaltranslation.com/about (with locale in a cookie)

Setting up locale routing with gt-next

First, nest your pages under a [locale] dynamic segment:

app/
└── [locale]/
    ├── layout.tsx
    ├── page.tsx
    └── about/
        └── page.tsx

Then create middleware in your project root (proxy.ts for Next.js 16+, or middleware.ts for Next.js 15 and below):

import { createNextMiddleware } from 'gt-next/middleware';

export default createNextMiddleware();

export const config = {
  matcher: ['/((?!api|static|.*\\..*|_next).*)'],
};

2. Setting the HTML `lang` attribute

The lang attribute on your <html> tag tells browsers and search engines which language the page is in. It's one of the simplest and most impactful things you can do for accessibility and SEO.

Without it, screen readers guess the language (often wrong), and search engines have less confidence in their language classification.

gt-next provides the useLocale hook that makes this trivial in your root layout:

import { useLocale, GTProvider } from 'gt-next';

export default function RootLayout({ children }: { children: React.ReactNode }) {
  const locale = useLocale();

  return (
    <html lang={locale}>
      <body>
        <GTProvider>
          {children}
        </GTProvider>
      </body>
    </html>
  );
}

useLocale returns the BCP 47 locale code (e.g., en-US, ar, zh-Hans).

3. Canonical URLs

Canonical tags tell search engines which URL is the "primary" version of a page. For multilingual sites, each language version should point to itself as the canonical:

<!-- On /fr/about -->
<link rel="canonical" href="https://example.com/fr/about" />

This prevents search engines from treating your French page as a duplicate of your English page.

In Next.js, you set canonicals through the metadata API. Combine it with gt-next's getLocale to generate the correct canonical for each locale:

import { getLocale } from 'gt-next/server';

const BASE_URL = 'https://example.com';

export async function generateMetadata() {
  const locale = await getLocale();

  return {
    alternates: {
      canonical: `${BASE_URL}/${locale}/about`,
    },
  };
}

export default function AboutPage() {
  return <h1>About Us</h1>;
}

For the default locale without a prefix, adjust accordingly:

import { getLocale, getDefaultLocale } from 'gt-next/server';

export async function generateMetadata() {
  const locale = await getLocale();
  const defaultLocale = getDefaultLocale();
  const path = '/about';

  const prefix = locale === defaultLocale ? '' : `/${locale}`;

  return {
    alternates: {
      canonical: `${BASE_URL}${prefix}${path}`,
    },
  };
}

4. Hreflang tags

Hreflang tags are the most important multilingual SEO signal. They tell search engines: "this page exists in these other languages, and here are the URLs."

Without hreflang, Google has to guess which language version to show in search results — and it often gets it wrong.

<link rel="alternate" hreflang="en" href="https://example.com/about" />
<link rel="alternate" hreflang="fr" href="https://example.com/fr/about" />
<link rel="alternate" hreflang="es" href="https://example.com/es/about" />
<link rel="alternate" hreflang="x-default" href="https://example.com/about" />

The x-default tag tells search engines which URL to show when none of the specified languages match the user.

In Next.js, you can add hreflang through the metadata API's alternates.languages property. Here's a reusable helper that works with gt-next:

import { getLocale, getDefaultLocale } from 'gt-next/server';

const BASE_URL = 'https://example.com';
const SUPPORTED_LOCALES = ['en', 'fr', 'es'];

export async function getI18NMetadata(path: string) {
  const locale = await getLocale();
  const defaultLocale = getDefaultLocale();

  const getUrl = (loc: string) => {
    const prefix = loc === defaultLocale ? '' : `/${loc}`;
    return `${BASE_URL}${prefix}${path}`;
  };

  const languages: Record<string, string> = {};
  for (const loc of SUPPORTED_LOCALES) {
    languages[loc] = getUrl(loc);
  }
  languages['x-default'] = getUrl(defaultLocale);

  return {
    alternates: {
      canonical: getUrl(locale),
      languages,
    },
  };
}

Then use it in any page:

import { getI18NMetadata } from '@/lib/i18n-metadata';

export async function generateMetadata() {
  return await getI18NMetadata('/about');
}

This generates both the canonical and all hreflang tags in one call.

5. Translated metadata

Search engines display your page title and description in results. If these are in English for a French page, users are less likely to click — and Google may demote the result.

Use gt-next's getGT function to translate metadata strings:

import { getGT } from 'gt-next/server';
import { getI18NMetadata } from '@/lib/i18n-metadata';

export async function generateMetadata() {
  const t = await getGT();
  const i18nMeta = await getI18NMetadata('/about');

  return {
    title: t('About Us'),
    description: t('Learn about our mission and team.'),
    ...i18nMeta,
  };
}

This gives you localized titles and descriptions in search results, which significantly improves click-through rates for non-English queries.

6. Multilingual sitemaps

A sitemap helps search engines discover all your pages, including every language version. For multilingual sites, you should include hreflang annotations in your sitemap as well.

Next.js supports programmatic sitemaps through a sitemap.ts file:

import { MetadataRoute } from 'next';

const BASE_URL = 'https://example.com';
const LOCALES = ['en', 'fr', 'es'];
const DEFAULT_LOCALE = 'en';
const PAGES = ['/', '/about', '/blog', '/contact'];

export default function sitemap(): MetadataRoute.Sitemap {
  return PAGES.flatMap((path) => {
    const getUrl = (locale: string) => {
      const prefix = locale === DEFAULT_LOCALE ? '' : `/${locale}`;
      return `${BASE_URL}${prefix}${path === '/' ? '' : path}`;
    };

    const languages: Record<string, string> = {};
    for (const locale of LOCALES) {
      languages[locale] = getUrl(locale);
    }

    return LOCALES.map((locale) => ({
      url: getUrl(locale),
      lastModified: new Date(),
      alternates: { languages },
    }));
  });
}

This generates a sitemap with one entry per page per locale, and each entry includes hreflang annotations pointing to all language versions.

Checklist

Here's a quick summary of everything covered:

SEO requirement	Implementation
Locale in URL	`createNextMiddleware()` with `[locale]` dynamic segment
HTML `lang` attribute	`useLocale()` in root layout
Canonical URLs	`getLocale()` + Next.js metadata API `alternates.canonical`
Hreflang tags	Next.js metadata API `alternates.languages` with all supported locales
Translated metadata	`getGT()` for page titles and descriptions
Multilingual sitemap	`sitemap.ts` with per-locale entries and hreflang alternates

Next steps

gt-next quickstart to set up the full i18n stack
Middleware guide for routing configuration
SSG guide for statically generating multilingual pages
RTL support for right-to-left languages

Back

How to Optimize SEO for a Multilingual Next.js App

February 17, 2026

General Translation

guideseointernationalizationnextjsi18nroutingmetadata

Why multilingual SEO needs special attention

A multilingual site without proper SEO setup has problems:

Google may index only one language version and ignore the rest
Users searching in Spanish get served the English page
Duplicate content penalties because Google sees /en/about and /fr/about as the same page
Incorrect language shown in search result snippets

The good news: getting multilingual SEO right in Next.js isn't complicated. There are five things you need to get right, and this guide covers all of them using gt-next.

1. Locale-based URL routing

The foundation of multilingual SEO is having distinct URLs for each language. Search engines need separate, crawlable URLs to index each language version independently.

This means locale-in-the-URL — not cookies, not query parameters, not Accept-Language detection alone.

✅ generaltranslation.com/en/about
✅ generaltranslation.com/fr/about
✅ generaltranslation.com/es/about

❌ generaltranslation.com/about?lang=fr
❌ generaltranslation.com/about (with locale in a cookie)

Setting up locale routing with gt-next

First, nest your pages under a [locale] dynamic segment:

app/
└── [locale]/
    ├── layout.tsx
    ├── page.tsx
    └── about/
        └── page.tsx

Then create middleware in your project root (proxy.ts for Next.js 16+, or middleware.ts for Next.js 15 and below):

import { createNextMiddleware } from 'gt-next/middleware';

export default createNextMiddleware();

export const config = {
  matcher: ['/((?!api|static|.*\\..*|_next).*)'],
};

2. Setting the HTML `lang` attribute

The lang attribute on your <html> tag tells browsers and search engines which language the page is in. It's one of the simplest and most impactful things you can do for accessibility and SEO.

Without it, screen readers guess the language (often wrong), and search engines have less confidence in their language classification.

gt-next provides the useLocale hook that makes this trivial in your root layout:

import { useLocale, GTProvider } from 'gt-next';

export default function RootLayout({ children }: { children: React.ReactNode }) {
  const locale = useLocale();

  return (
    <html lang={locale}>
      <body>
        <GTProvider>
          {children}
        </GTProvider>
      </body>
    </html>
  );
}

useLocale returns the BCP 47 locale code (e.g., en-US, ar, zh-Hans).

3. Canonical URLs

Canonical tags tell search engines which URL is the "primary" version of a page. For multilingual sites, each language version should point to itself as the canonical:

<!-- On /fr/about -->
<link rel="canonical" href="https://example.com/fr/about" />

This prevents search engines from treating your French page as a duplicate of your English page.

In Next.js, you set canonicals through the metadata API. Combine it with gt-next's getLocale to generate the correct canonical for each locale:

import { getLocale } from 'gt-next/server';

const BASE_URL = 'https://example.com';

export async function generateMetadata() {
  const locale = await getLocale();

  return {
    alternates: {
      canonical: `${BASE_URL}/${locale}/about`,
    },
  };
}

export default function AboutPage() {
  return <h1>About Us</h1>;
}

For the default locale without a prefix, adjust accordingly:

import { getLocale, getDefaultLocale } from 'gt-next/server';

export async function generateMetadata() {
  const locale = await getLocale();
  const defaultLocale = getDefaultLocale();
  const path = '/about';

  const prefix = locale === defaultLocale ? '' : `/${locale}`;

  return {
    alternates: {
      canonical: `${BASE_URL}${prefix}${path}`,
    },
  };
}

4. Hreflang tags

Hreflang tags are the most important multilingual SEO signal. They tell search engines: "this page exists in these other languages, and here are the URLs."

Without hreflang, Google has to guess which language version to show in search results — and it often gets it wrong.

<link rel="alternate" hreflang="en" href="https://example.com/about" />
<link rel="alternate" hreflang="fr" href="https://example.com/fr/about" />
<link rel="alternate" hreflang="es" href="https://example.com/es/about" />
<link rel="alternate" hreflang="x-default" href="https://example.com/about" />

The x-default tag tells search engines which URL to show when none of the specified languages match the user.

In Next.js, you can add hreflang through the metadata API's alternates.languages property. Here's a reusable helper that works with gt-next:

import { getLocale, getDefaultLocale } from 'gt-next/server';

const BASE_URL = 'https://example.com';
const SUPPORTED_LOCALES = ['en', 'fr', 'es'];

export async function getI18NMetadata(path: string) {
  const locale = await getLocale();
  const defaultLocale = getDefaultLocale();

  const getUrl = (loc: string) => {
    const prefix = loc === defaultLocale ? '' : `/${loc}`;
    return `${BASE_URL}${prefix}${path}`;
  };

  const languages: Record<string, string> = {};
  for (const loc of SUPPORTED_LOCALES) {
    languages[loc] = getUrl(loc);
  }
  languages['x-default'] = getUrl(defaultLocale);

  return {
    alternates: {
      canonical: getUrl(locale),
      languages,
    },
  };
}

Then use it in any page:

import { getI18NMetadata } from '@/lib/i18n-metadata';

export async function generateMetadata() {
  return await getI18NMetadata('/about');
}

This generates both the canonical and all hreflang tags in one call.

5. Translated metadata

Search engines display your page title and description in results. If these are in English for a French page, users are less likely to click — and Google may demote the result.

Use gt-next's getGT function to translate metadata strings:

import { getGT } from 'gt-next/server';
import { getI18NMetadata } from '@/lib/i18n-metadata';

export async function generateMetadata() {
  const t = await getGT();
  const i18nMeta = await getI18NMetadata('/about');

  return {
    title: t('About Us'),
    description: t('Learn about our mission and team.'),
    ...i18nMeta,
  };
}

This gives you localized titles and descriptions in search results, which significantly improves click-through rates for non-English queries.

6. Multilingual sitemaps

A sitemap helps search engines discover all your pages, including every language version. For multilingual sites, you should include hreflang annotations in your sitemap as well.

Next.js supports programmatic sitemaps through a sitemap.ts file:

import { MetadataRoute } from 'next';

const BASE_URL = 'https://example.com';
const LOCALES = ['en', 'fr', 'es'];
const DEFAULT_LOCALE = 'en';
const PAGES = ['/', '/about', '/blog', '/contact'];

export default function sitemap(): MetadataRoute.Sitemap {
  return PAGES.flatMap((path) => {
    const getUrl = (locale: string) => {
      const prefix = locale === DEFAULT_LOCALE ? '' : `/${locale}`;
      return `${BASE_URL}${prefix}${path === '/' ? '' : path}`;
    };

    const languages: Record<string, string> = {};
    for (const locale of LOCALES) {
      languages[locale] = getUrl(locale);
    }

    return LOCALES.map((locale) => ({
      url: getUrl(locale),
      lastModified: new Date(),
      alternates: { languages },
    }));
  });
}

This generates a sitemap with one entry per page per locale, and each entry includes hreflang annotations pointing to all language versions.

Checklist

Here's a quick summary of everything covered:

SEO requirement	Implementation
Locale in URL	`createNextMiddleware()` with `[locale]` dynamic segment
HTML `lang` attribute	`useLocale()` in root layout
Canonical URLs	`getLocale()` + Next.js metadata API `alternates.canonical`
Hreflang tags	Next.js metadata API `alternates.languages` with all supported locales
Translated metadata	`getGT()` for page titles and descriptions
Multilingual sitemap	`sitemap.ts` with per-locale entries and hreflang alternates

Next steps

gt-next quickstart to set up the full i18n stack
Middleware guide for routing configuration
SSG guide for statically generating multilingual pages
RTL support for right-to-left languages

Back

How to Optimize SEO for a Multilingual Next.js App

February 17, 2026

General Translation

guideseointernationalizationnextjsi18nroutingmetadata

Why multilingual SEO needs special attention

A multilingual site without proper SEO setup has problems:

Google may index only one language version and ignore the rest
Users searching in Spanish get served the English page
Duplicate content penalties because Google sees /en/about and /fr/about as the same page
Incorrect language shown in search result snippets

The good news: getting multilingual SEO right in Next.js isn't complicated. There are five things you need to get right, and this guide covers all of them using gt-next.

1. Locale-based URL routing

The foundation of multilingual SEO is having distinct URLs for each language. Search engines need separate, crawlable URLs to index each language version independently.

This means locale-in-the-URL — not cookies, not query parameters, not Accept-Language detection alone.

✅ generaltranslation.com/en/about
✅ generaltranslation.com/fr/about
✅ generaltranslation.com/es/about

❌ generaltranslation.com/about?lang=fr
❌ generaltranslation.com/about (with locale in a cookie)

Setting up locale routing with gt-next

First, nest your pages under a [locale] dynamic segment:

app/
└── [locale]/
    ├── layout.tsx
    ├── page.tsx
    └── about/
        └── page.tsx

Then create middleware in your project root (proxy.ts for Next.js 16+, or middleware.ts for Next.js 15 and below):

import { createNextMiddleware } from 'gt-next/middleware';

export default createNextMiddleware();

export const config = {
  matcher: ['/((?!api|static|.*\\..*|_next).*)'],
};

2. Setting the HTML `lang` attribute

The lang attribute on your <html> tag tells browsers and search engines which language the page is in. It's one of the simplest and most impactful things you can do for accessibility and SEO.

Without it, screen readers guess the language (often wrong), and search engines have less confidence in their language classification.

gt-next provides the useLocale hook that makes this trivial in your root layout:

import { useLocale, GTProvider } from 'gt-next';

export default function RootLayout({ children }: { children: React.ReactNode }) {
  const locale = useLocale();

  return (
    <html lang={locale}>
      <body>
        <GTProvider>
          {children}
        </GTProvider>
      </body>
    </html>
  );
}

useLocale returns the BCP 47 locale code (e.g., en-US, ar, zh-Hans).

3. Canonical URLs

Canonical tags tell search engines which URL is the "primary" version of a page. For multilingual sites, each language version should point to itself as the canonical:

<!-- On /fr/about -->
<link rel="canonical" href="https://example.com/fr/about" />

This prevents search engines from treating your French page as a duplicate of your English page.

In Next.js, you set canonicals through the metadata API. Combine it with gt-next's getLocale to generate the correct canonical for each locale:

import { getLocale } from 'gt-next/server';

const BASE_URL = 'https://example.com';

export async function generateMetadata() {
  const locale = await getLocale();

  return {
    alternates: {
      canonical: `${BASE_URL}/${locale}/about`,
    },
  };
}

export default function AboutPage() {
  return <h1>About Us</h1>;
}

For the default locale without a prefix, adjust accordingly:

import { getLocale, getDefaultLocale } from 'gt-next/server';

export async function generateMetadata() {
  const locale = await getLocale();
  const defaultLocale = getDefaultLocale();
  const path = '/about';

  const prefix = locale === defaultLocale ? '' : `/${locale}`;

  return {
    alternates: {
      canonical: `${BASE_URL}${prefix}${path}`,
    },
  };
}

4. Hreflang tags

Hreflang tags are the most important multilingual SEO signal. They tell search engines: "this page exists in these other languages, and here are the URLs."

Without hreflang, Google has to guess which language version to show in search results — and it often gets it wrong.

<link rel="alternate" hreflang="en" href="https://example.com/about" />
<link rel="alternate" hreflang="fr" href="https://example.com/fr/about" />
<link rel="alternate" hreflang="es" href="https://example.com/es/about" />
<link rel="alternate" hreflang="x-default" href="https://example.com/about" />

The x-default tag tells search engines which URL to show when none of the specified languages match the user.

In Next.js, you can add hreflang through the metadata API's alternates.languages property. Here's a reusable helper that works with gt-next:

import { getLocale, getDefaultLocale } from 'gt-next/server';

const BASE_URL = 'https://example.com';
const SUPPORTED_LOCALES = ['en', 'fr', 'es'];

export async function getI18NMetadata(path: string) {
  const locale = await getLocale();
  const defaultLocale = getDefaultLocale();

  const getUrl = (loc: string) => {
    const prefix = loc === defaultLocale ? '' : `/${loc}`;
    return `${BASE_URL}${prefix}${path}`;
  };

  const languages: Record<string, string> = {};
  for (const loc of SUPPORTED_LOCALES) {
    languages[loc] = getUrl(loc);
  }
  languages['x-default'] = getUrl(defaultLocale);

  return {
    alternates: {
      canonical: getUrl(locale),
      languages,
    },
  };
}

Then use it in any page:

import { getI18NMetadata } from '@/lib/i18n-metadata';

export async function generateMetadata() {
  return await getI18NMetadata('/about');
}

This generates both the canonical and all hreflang tags in one call.

5. Translated metadata

Search engines display your page title and description in results. If these are in English for a French page, users are less likely to click — and Google may demote the result.

Use gt-next's getGT function to translate metadata strings:

import { getGT } from 'gt-next/server';
import { getI18NMetadata } from '@/lib/i18n-metadata';

export async function generateMetadata() {
  const t = await getGT();
  const i18nMeta = await getI18NMetadata('/about');

  return {
    title: t('About Us'),
    description: t('Learn about our mission and team.'),
    ...i18nMeta,
  };
}

This gives you localized titles and descriptions in search results, which significantly improves click-through rates for non-English queries.

6. Multilingual sitemaps

A sitemap helps search engines discover all your pages, including every language version. For multilingual sites, you should include hreflang annotations in your sitemap as well.

Next.js supports programmatic sitemaps through a sitemap.ts file:

import { MetadataRoute } from 'next';

const BASE_URL = 'https://example.com';
const LOCALES = ['en', 'fr', 'es'];
const DEFAULT_LOCALE = 'en';
const PAGES = ['/', '/about', '/blog', '/contact'];

export default function sitemap(): MetadataRoute.Sitemap {
  return PAGES.flatMap((path) => {
    const getUrl = (locale: string) => {
      const prefix = locale === DEFAULT_LOCALE ? '' : `/${locale}`;
      return `${BASE_URL}${prefix}${path === '/' ? '' : path}`;
    };

    const languages: Record<string, string> = {};
    for (const locale of LOCALES) {
      languages[locale] = getUrl(locale);
    }

    return LOCALES.map((locale) => ({
      url: getUrl(locale),
      lastModified: new Date(),
      alternates: { languages },
    }));
  });
}

This generates a sitemap with one entry per page per locale, and each entry includes hreflang annotations pointing to all language versions.

Checklist

Here's a quick summary of everything covered:

SEO requirement	Implementation
Locale in URL	`createNextMiddleware()` with `[locale]` dynamic segment
HTML `lang` attribute	`useLocale()` in root layout
Canonical URLs	`getLocale()` + Next.js metadata API `alternates.canonical`
Hreflang tags	Next.js metadata API `alternates.languages` with all supported locales
Translated metadata	`getGT()` for page titles and descriptions
Multilingual sitemap	`sitemap.ts` with per-locale entries and hreflang alternates

Next steps

gt-next quickstart to set up the full i18n stack
Middleware guide for routing configuration
SSG guide for statically generating multilingual pages
RTL support for right-to-left languages