Translating Shared Strings

Overview

Shared strings are strings or constants that are used in multiple places in your app.

For example, you may have a string that is used in multiple components, or a constant that is used in multiple files.

In traditional i18n libraries, you would need to create a dictionary for each shared string.

This guide will walk you through how to easily internationalize shared strings in your Next.js app using the msg() function & useMessages() hook.

We will cover the following:

When to use the msg() function

How to use the msg() function and useMessages() hook

Using variables

Examples

Common pitfalls

When to use the `msg()` function

The msg() function is a simple function that is used to mark strings for translation.

Let's look at an example of a shared object containing strings:

src/navData.ts

export const navData = {
  home: {
    label: 'Home',
    description: 'The home page',
    icon: 'home',
    href: '/',
  },
  about: {
    label: 'About',
    description: 'Information about the company',
    icon: 'info',
    href: '/about',
  },
}

Normally, to internationalize this object, you would need to either create a dictionary entry for each string, or refactor your object into a function that returns the data with translations.

For example, you might have:

src/navData.ts

export const getNavData = (t: (content: string) => string) => ({
  home: {
    label: t('Home'),
    description: t('The home page'),
    icon: 'home',
    href: '/',
  },
  about: {
    label: t('About'),
    description: t('Information about the company'),
    icon: 'info',
    href: '/about',
  },
})

Everywhere else in your app where navData was imported, you would need to call getNavData(t) instead.

src/app/page.tsx

import { getNavData } from '@/navData';

export default function Home() {
  const t = useGT();
  const navData = getNavData(t);
  return <div>{navData.home.label}</div>;
}

This can lead to a lot of work. The solution is to use the msg() function.

How to use the `msg()` function

To use the msg() function, pass the string directly to the function. The function returns a special, encoded string that can be used for translations.

src/navData.ts

import { msg } from 'gt-next';

export const navData = [
  {
    label: msg('Home'), // Output has type `string`
    description: msg('The home page'),
    icon: 'home',
    href: '/',
  },
  {
    label: msg('About'),
    description: msg('Information about the company'),
    icon: 'info',
    href: '/about',
  },
]

Then, simply pass the encoded string to the useMessages() hook.

src/app/page.tsx

import { useMessages } from 'gt-next';
import { navData } from '@/navData';

export default function Home() {
  const m = useMessages();
  return (
    <div>
      {navData.map((item) => (
        <div key={item.label}>{m(item.label)}</div>
      ))}
    </div>
  );
}

If you are in an async component, use the getMessages() function instead of the useMessages() hook.

src/app/page.tsx

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

export default async function Home() {
  const m = await getMessages();
  return (
    <div>
      {navData.map((item) => (
        <div key={item.label}>{m(item.label)}</div>
      ))}
    </div>
  );
}

Beware! The string returned by the msg() function is encoded and will be different from the original input string. If want to get back the original string, you need to decode it with decodeMsg()

Using variables

If your string is a template string and contains variables, you can pass the variables to the msg() function.

Simply change the ${} notation in the template string to {variable}, and pass an object as the second argument to msg() with the variable name as the key.

src/navData.ts

const items = 100;
export const pricing = [
  {
    name: 'Basic',
    price: 100,
    description: `The basic plan includes ${items} items`
  },
]

Should be turned into:

src/navData.ts

import { msg } from 'gt-next';

const items = 100;
export const pricing = [
  {
    name: 'Basic',
    price: 100,
    description: msg('The basic plan includes {items} items', { items })
  },
]

The {items} placeholder will be replaced with the value of the items variable.

This allows you to display dynamic values in your translations.

For more information on the API, see the API reference.

gt-next supports ICU message format, which allows you to also format your variables.

const price = 100;
msg('There are {count, plural, =0 {no items} =1 {one item} other {{count} items}} in the cart', { count: 10 });

ICU message format is a powerful way to format your variables. For more information, see the ICU message format documentation.

Examples

Translating a shared global object

src/llms.ts

import { msg } from 'gt-next';

export const llmData = [
  {
    name: 'GPT-4.1',
    id: 'gpt-4.1',
    description: msg('GPT-4.1 is a large language model developed by OpenAI'),
  },
  {
    name: 'Claude 3.7 Sonnet',
    id: 'claude-3-7-sonnet',
    description: msg('Claude 3.7 Sonnet is a large language model developed by Anthropic'),
  },
];

src/app/page.tsx

import { llmData } from '@/llms';
import { useMessages } from 'gt-next';

export default function MyComponent() {
  const m = useMessages();
  return (
    <div>
      {llmData.map((llm) => (
        <div key={llm.id}>
          <h1>{llm.name}</h1>
          <p>{m(llm.description)}</p>
        </div>
      ))}
    </div>
  )
}

src/llms.ts

export const llms = [
  {
    name: 'GPT-4.1',
    id: 'gpt-4.1',
    description: 'GPT-4.1 is a large language model developed by OpenAI',
  },
  {
    name: 'Claude 3.7 Sonnet',
    id: 'claude-3-7-sonnet',
    description: 'Claude 3.7 Sonnet is a large language model developed by Anthropic',
  },
]

src/app/page.tsx

import { llms } from '@/llms';

export default function MyComponent() {
  return (
    <div>
      {llms.map((llm) => (
        <div key={llm.id}>
          <h1>{llm.name}</h1>
          <p>{llm.description}</p>
        </div>
      ))}
    </div>
  )
}

Translating a function's return value

src/llms.ts

import { msg } from 'gt-next';

function mockData() {
  return [
    {
      name: 'GPT-4.1',
      id: 'gpt-4.1',
      company: 'OpenAI',
    },
    {
      name: 'Claude 3.7 Sonnet',
      id: 'claude-3-7-sonnet',
      company: 'Anthropic',
    },
  ];
}

export function getData() {
  const data = mockData();
  const modifiedData = data.map((item) => ({
    ...item,
    description: msg('{name} is a large language model developed by {company}', {
      name: item.name,
      company: item.company,
    }),
  }));
  return modifiedData;
}

src/app/page.tsx

import { getData } from '@/llms';
import { useMessages } from 'gt-next';

export default function MyComponent() {
  const m = useMessages();
  const data = getData();
  return (
    <div>
      {data.map((item) => (
        <div key={item.id}>
          <h1>{item.name}</h1>
          <p>{m(item.description)}</p>
        </div>
      ))}
    </div>
  )
}

src/llms.ts

import { msg } from 'gt-next';

function mockData() {
  return [
    {
      name: 'GPT-4.1',
      id: 'gpt-4.1',
      company: 'OpenAI',
    },
    {
      name: 'Claude 3.7 Sonnet',
      id: 'claude-3-7-sonnet',
      company: 'Anthropic',
    },
  ];
}

export function getData() {
  const data = mockData();
  const modifiedData = data.map((item) => ({
    ...item,
    description: `${item.name} is a large language model developed by ${item.company}`,
  }));
  return modifiedData;
}

src/app/page.tsx

import { getData } from '@/llms';

export default function MyComponent() {
  const data = getData();
  return (
    <div>
      {data.map((item) => (
        <div key={item.id}>
          <h1>{item.name}</h1>
          <p>{item.description}</p>
        </div>
      ))}
    </div>
  )
}

Common Pitfalls

Forgetting to call `useMessages()`

msg() encodes the input string, so you cannot use it directly in JSX or elsewhere.

If you attempt to use the encoded string directly, you will get a weird string that looks something like this:

const encodedString = msg('Hello, world!');
console.log(encodedString); // "Hello, world!:eyIkX2hhc2giOiJkMjA3MDliZGExNjNlZmM2In0="

To fix this, you need to use the useMessages() hook to get the translated string.

import { useMessages } from 'gt-next';

const encodedString = msg('Hello, world!');

export default function MyComponent() {
  const m = useMessages();
  return <div>{m(encodedString)}</div>; // 'Hello, world!' in the current language
}

Alternatively, if you want to recover the original string, you can use the decodeMsg() function.

import { decodeMsg } from 'gt-next';

const encodedString = msg('Hello, world!');
const decodedString = decodeMsg(encodedString);
console.log(decodedString); // "Hello, world!"

Wrapping dynamic content in `msg()`

All strings must be known at build time. This means that you cannot wrap dynamic content in msg().

For example, this is invalid:

const dynamicContent = msg(`Hello, ${name}`);

To fix this, provide the dynamic content as a variable, and then pass it to msg().

const dynamicContent = msg('Hello, {name}', { name });

The CLI tool will warn you if you try to wrap dynamic content with msg().

Next Steps

See the API reference for msg().
See the API reference for useMessages().
Learn more about the <T> component.

Translating Shared Strings

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