How to Add next-intl Internationalization to Next.js 15: Step-by-Step Guide

Internationalization (i18n) is essential for modern web apps. With Next.js 15, the recommended way to add i18n is using next-intl. In this guide, you'll learn how to set up next-intl in a Next.js 15 project with a working, real-world approach.

🚀 Looking for a Next.js Template with next-intl Already Integrated?

If you want to skip the setup and start with a production-ready template that already includes next-intl internationalization, check out our Next.js Financial Dashboard Template.

🎯 This premium template comes with:

• ✅ next-intl already configured and ready to use
• ✅ Dark/Light theme switching
• ✅ Redux Toolkit state management
• ✅ Modern financial dashboard UI
• ✅ Email authentication
• ✅ Responsive design
• ✅ TypeScript support

Perfect for fintech applications, banking dashboards, and financial management systems.

View Demo | Get Template

---

1. Install next-intl

First, install the package:

npm install next-intl

2. Configure Routing

Create a routing config to define your supported locales. In Aniq-UI, this is done in src/i18n/routing.ts:

// src/i18n/routing.ts
import {defineRouting} from 'next-intl/routing';

export const routing = defineRouting({
  locales: ['en', 'fr', 'ar', 'es'],
  defaultLocale: 'en'
});

3. Add Navigation Helpers

Set up navigation helpers in src/i18n/navigation.ts:

// src/i18n/navigation.ts
import { createNavigation } from 'next-intl/navigation';
import { routing } from './routing';

export const { Link, redirect, usePathname, useRouter, getPathname } = createNavigation(routing);

4. Load Messages on the Server

Configure message loading in src/i18n/request.ts:

// src/i18n/request.ts
import { getRequestConfig } from 'next-intl/server';
import { hasLocale } from 'next-intl';
import { routing } from './routing';

export default getRequestConfig(async ({ requestLocale }) => {
    const requested = await requestLocale;
    const locale = hasLocale(routing.locales, requested)
        ? requested
        : routing.defaultLocale;

    const [seoMessages] = await Promise.all([
        import(`../messages/seo/${locale}.json`).then(module => module.default).catch(() => ({})),
    ]);

    return {
        locale,
        messages: {
            seo: seoMessages,
        }
    };
});

5. Provide Messages to Your App

Wrap your pages with NextIntlClientProvider. For example, in src/app/[locale]/about/layout.tsx:

// src/app/[locale]/about/layout.tsx
import { NextIntlClientProvider } from "next-intl";

export default async function AboutLayout({
  children,
  params,
}: {
  children: React.ReactNode;
  params: Promise<{ locale: string }>;
}) {
  const { locale } = await params;

  const [about] = await Promise.all([
    import(`@/messages/about/${locale}.json`).then((mod) => mod.default),
  ]);

  const messages = { about };
  return (
    <NextIntlClientProvider locale={locale} messages={messages}>
      {children}
    </NextIntlClientProvider>
  );
}

6. Organize Your Message Files

Store your translation files in src/messages/, e.g.:

src/messages/about/en.json
src/messages/about/fr.json
src/messages/about/ar.json
src/messages/about/es.json

Each file contains translations for a namespace, e.g.:

{
  "header_story": "Our Story",
  "header_title1": "We're Building",
  // ...
}

7. Use Translations in Components

Use the useTranslations hook from next-intl:

import { useTranslations } from "next-intl";

export default function AboutHeader() {
  const t = useTranslations("about");
  return <h1>{t("header_title1")}</h1>;
}

8. Add a Language Switcher

Here is the full code for the src/components/LanguageSelector/index.tsx component used in Aniq-UI:

// filepath: src/components/LanguageSelector/index.tsx
"use client";

import React, { useState, useRef, useEffect } from "react";
import { useParams, useRouter } from "next/navigation";
import { cn } from "@/lib/utils";
import { IconLanguage, IconChevronDown } from "@/lib/icons";

interface Language {
  code: string;
  name: string;
  rtl: boolean;
}

const languages: Language[] = [
  { code: "en", name: "English", rtl: false },
  { code: "fr", name: "Français", rtl: false },
  { code: "es", name: "Español", rtl: false },
  { code: "ar", name: "العربية", rtl: true },
];

export default function LanguageSelector() {
  const [isOpen, setIsOpen] = useState(false);
  const dropdownRef = useRef<HTMLDivElement>(null);
  const router = useRouter();
  const params = useParams();
  const currentLocale = typeof params.locale === "string" ? params.locale : "en";
  
  const currentLanguage = languages.find((lang) => lang.code === currentLocale) || languages[0];

  useEffect(() => {
    const handleClickOutside = (event: MouseEvent) => {
      if (
        dropdownRef.current &&
        !dropdownRef.current.contains(event.target as Node)
      ) {
        setIsOpen(false);
      }
    };

    document.addEventListener("mousedown", handleClickOutside);
    return () => {
      document.removeEventListener("mousedown", handleClickOutside);
    };
  }, []);

  const changeLanguage = (langCode: string) => {
    const currentPath = window.location.pathname;
    // Extract the path after the locale segment
    const pathSegments = currentPath.split('/');
    pathSegments[1] = langCode; // Replace the locale segment
    
    const newPath = pathSegments.join('/');
    router.push(newPath);
    setIsOpen(false);
  };

  return (
    <div className="relative" ref={dropdownRef}>
      <button
        onClick={() => setIsOpen(!isOpen)}
        className="flex items-center  cursor-pointer px-2 py-2 rounded-md hover:bg-gray-100 dark:hover:bg-gray-800 text-sm"
        aria-expanded={isOpen}
        aria-haspopup="true"
      >
        <IconLanguage className="w-4 h-4 mr-1" />
        <span className="font-medium text-xs mr-1">{currentLanguage.code.toUpperCase()}</span>
        <IconChevronDown className={cn("w-3 h-3 transition-transform", isOpen ? "rotate-180" : "")} />
      </button>

      {isOpen && (
        <div className="absolute z-50 mt-1 bg-white dark:bg-neutral-900 border border-gray-200 dark:border-gray-700 rounded-md shadow-lg py-1 w-40 min-w-max right-0">
          <ul className="py-1">
            {languages.map((language) => (
              <li key={language.code}>
                <button
                  onClick={() => changeLanguage(language.code)}
                  className={cn(
                    "w-full text-left cursor-pointer px-4 py-2 text-sm hover:bg-gray-100 dark:hover:bg-gray-800 flex items-center",
                    language.code === currentLocale && "bg-gray-100 dark:bg-gray-800"
                  )}
                 >
                  <span className="inline-block me-2 w-max font-medium text-xs">{language.code.toUpperCase()}</span>
                  {language.name}
                </button>
              </li>
            ))}
          </ul>
        </div>
      )}
    </div>
  );
}

9. Test Your Setup

Start your dev server and visit /en/about, /fr/about, etc. You should see the correct translations and be able to switch languages.

Conclusion

With next-intl, adding internationalization to Next.js 15 is straightforward and powerful. For a full working example, explore the Aniq-UI repository.

---

References:

• next-intl Documentation
• Next.js Internationalization