next-multilingual
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An opinionated end-to-end solution for Next.js applications that requires multiple languages.
next-multilingual is an opinionated end-to-end solution for Next.js applications ✱ that requires multiple languages.
Check out our demo app!
✱ next-multilingual only works with 📁 pages directory. We are still ironing out our solution to support the new 📁 app directory since internationalization is no longer part of Next.js' config.
npm install next-multilingual
useMessages hook that supports ICU MessageFormat and JSX injection out of the box./en-us/contact-us for U.S. English and /fr-ca/nous-joindre for Canadian French) ✱.✱ Your default locale slugs must match the pages directory file system (e.g., a slug for "About us" should be in an about-us directory). If the default locale you require uses characters beyond those supported by the file system, it hasn't been tested and will likely not work. Pull requests are welcome 😊.
next-multilingual has put a lot of effort into adding TSDoc to all its APIs. Please check directly in your IDE if you are unsure how to use certain APIs provided in our examples.
Also, having an opinion on "best practices" is not an easy task. This is why we documented our design decisions in a special document that can be consulted here. If you feel that some of our APIs don't offer what you would expect, make sure to consult this document before opening an issue.
For those who prefer to jump right into the action, look in the example directory for an end-to-end implementation of next-multilingual. For the rest, the section below will provide a complete, step by step, configuration guide.
There are many options to configure in Next.js to achieve our goals. next-multilingual mostly cares about:
We offer two APIs to simplify this step:
getConfig (simple config)This function will generate a Next.js config that will meet most use cases. getConfig takes the following arguments:
applicationId — The unique application identifier that will be used as a messages key prefix.locales — The locales of your application.defaultLocale - The default locale of your application (it must also be included in locales)
❗ Only BCP 47 language tags following the
language-countryformat are accepted. For more details on why, refer to the design decisions document.
options (optional) — Options part of a Next.js configuration object.getConfig will return a Next.js configuration object.
To use it, simply add the following code in your application's next.config.js:
const { getConfig } = require('next-multilingual/config')
const config = getConfig('exampleApp', ['en-US', 'fr-CA'], 'en-US', {
// Put your optional options below.
poweredByHeader: false,
})
module.exports = config
Not all configuration options are not supported by getConfig. If you ever happen to use one, an error message will point you directly to the next section: advanced config.
Config (advanced config)If you have more advanced needs, you can use the Config object directly and insert the configuration required by next-multilingual directly in an existing next.config.js. The arguments of Config are almost identical to getConfig (minus the options) - check in your IDE (TSDoc) for details. Here is an example of how it can be used:
const { Config, webpackConfigurationHandler } = require('next-multilingual/config')
const config = new Config('exampleApp', ['en-US', 'fr-CA'], 'en-US')
module.exports = {
reactStrictMode: true,
i18n: {
locales: config.getUrlLocalePrefixes(),
defaultLocale: config.getDefaultUrlLocalePrefix(),
localeDetection: false,
},
poweredByHeader: false,
webpack: webpackConfigurationHandler,
}
If you need to customize your own Webpack configuration, we recommend extending our handler like this:
import Webpack from 'webpack'
import { webpackConfigurationHandler, WebpackContext } from 'next-multilingual/config'
export const myWebpackConfigurationHandler = (
config: Webpack.Configuration,
context: WebpackContext
): Webpack.Configuration => {
const myConfig = webpackConfigurationHandler(config, context)
// Do stuff here.
return myConfig
}
Or directly in next.config.js:
// Webpack handler wrapping next-multilingual's handler.
const webpack = (config, context) => {
config = webpackConfigurationHandler(config, context)
// Do stuff here.
return config
}
next-multilingual/config does 2 things leveraging Next.js' current routing capability:
next-multilingual/config also handles the special Webpack configuration required for server side rendering of localized
URLs using next-multilingual/link/ssr for Link components and next-multilingual/head/ssr for canonical and alternate links in the Head component.
For more details on the implementation such as why we are using UTF-8 characters, refer to the design decisions document.
next-multilingual/messages/babel-pluginTo display localized messages with the useMessages() hook, we need to configure our custom Babel plugin that will automatically inject strings into pages and components. The recommended way to do this is to include a .babelrc at the base of your application:
{
"presets": ["next/babel"],
"plugins": ["next-multilingual/messages/babel-plugin"]
}
If you do not configure the plugin you will get an error when trying to use useMessages.
App (_app.tsx)We need to create a custom App by adding _app.tsx in the pages directory:
import { useActualLocale } from 'next-multilingual'
import type { AppProps } from 'next/app'
const ExampleApp: React.FC<AppProps> = ({ Component, pageProps }) => {
useActualLocale() // Forces Next.js to use the actual (proper) locale.
return <Component {...pageProps} />
}
export default ExampleApp
This basically does two things, as mentioned in the comments:
/). If you do not want to use next-multilingual's locale detection you can use useActualLocale(false) instead.Document (_document.tsx)We also need to create a custom Document by adding _document.tsx in the pages directory:
import { getHtmlLang } from 'next-multilingual'
import { DocumentProps, Head, Html, Main, NextScript } from 'next/document'
const Document: React.FC<DocumentProps> = (documentProps) => {
return (
<Html lang={getHtmlLang(documentProps)} translate="no" className="notranslate">
<Head>
<meta name="google" content="notranslate" />
</Head>
<body>
<Main />
<NextScript />
</body>
</Html>
)
}
export default Document
This serves only 1 purpose: display the correct server side locale in the <html> tag. Since we are using a "fake" default locale, it's important to keep the correct SSR markup, especially when resolving a dynamic locale on /.
next-multilingual/head provides a <Head> component which automatically creates a canonical link and alternate links in the header. This is something that is not provided out of the box by Next.js.
NEXT_PUBLIC_ORIGIN environment variableAs per Google, alternate links must be fully-qualified, including the transport method (http/https). Because Next.js does not know which URL is used at build time, we need to specify the absolute URL that will be used, in an environment variable. For example, for the development environment, create an .env.development file at the root of your application with the following variable (adjust based on your setup):
NEXT_PUBLIC_ORIGIN=http://localhost:3000
Regardless of the environment, next-multilingual will look for a variable called NEXT_PUBLIC_ORIGIN to generate fully-qualified URLs. If you are using Next.js' basePath, it will be added automatically to the base URL.
NEXT_PUBLIC_ORIGIN will only accept fully qualified domains (e.g., http://example.com), without any paths.
next-multilingual 🎬Now that everything has been configured, we can focus on using next-multilingual!
In order to get next-multilingual to work as designed, we had to find solutions to 2 problems:
undefined values: because Next.js support sites without locales, it's native types allows to have undefined values, which for our case is more of an annoyance and requires extra casting.next-multilingual has to create a default locale that we never use. This means that to access the relevant locale information, we cannot rely on Next.js' APIs.We created the following APIs to allow consistent locales values across your application:
useRouterThis is a simple wrapper on top of Next.js' useRouter which both provides the correct locales but also never returns undefined.
import { NextPage } from 'next'
import { useRouter } from 'next-multilingual/router'
const Page: NextPage = () => {
const router = useRouter()
return <>{router.locale}</>
}
export default Page
getStaticPropsLocalesimport { getStaticPropsLocales } from 'next-multilingual'
export const getStaticProps: GetStaticProps = async (context) => {
const { locale, locales, defaultLocale } = getStaticPropsLocales(context)
// do stuff
return { props: {} }
}
getStaticPathsLocalesimport { getStaticPathsLocales } from 'next-multilingual'
export const getStaticPaths: GetStaticProps = async (context) => {
const { locales, defaultLocale } = getStaticPathsLocales(context)
// do stuff
return { props: {} }
}
getServerSidePropsLocalesimport { getServerSidePropsLocales } from 'next-multilingual'
export const getServerSideProps: GetServerSideProps = async (context) => {
const { locale, locales, defaultLocale } = getServerSidePropsLocales(context)
// do stuff
return { props: {} }
}
⚠️ Note that while we recommend using smart locale detection to dynamically render the homepage, this is completely optional. By using advanced configuration with
localeDetection: true, you will restore the default Next.js behavior without the need of usinggetServerSideProps.
The homepage is a bit more complex than other pages, because we need to implement dynamic locale detection (and display) for the following reason:
/ can have a negative impact on SEO and is not the best user experience.next-multilingual comes with a getPreferredLocale API that offers smarter auto-detection than the default Next.js implementation.You can find a full implementation in the example, but here is a stripped down version:
import type { GetServerSideProps, NextPage } from 'next'
import { ResolvedLocaleServerSideProps, resolveLocale, useResolvedLocale } from 'next-multilingual'
import { useRouter } from 'next-multilingual/router'
const Homepage: NextPage<ResolvedLocaleServerSideProps> = ({ resolvedLocale }) => {
// Force Next.js to use a locale that was resolved dynamically on the homepage (this must be the first action on the homepage).
useResolvedLocale(resolvedLocale)
const { locale } = useRouter()
return <h1>{locale}</h1>
}
export default Homepage
export const getServerSideProps: GetServerSideProps<ResolvedLocaleServerSideProps> = async (
context
) => {
return {
props: {
resolvedLocale: resolveLocale(context),
},
}
}
In a nutshell, this is what is happening:
next-multilingual's locale cookie.useResolvedLocale to make this dynamic across the application.Every time that you create a tsx, ts, jsx or js (compilable) file and that you need localized messages, you can simply create a message file in your supported locales that will only be usable by these files. Just like CSS modules, the idea is that you can have message files associated with another file's local scope. This has the benefit of making messages more modular and also avoids sharing messages across different contexts (more details in the design decisions document on why this is bad).
Message files have 2 main use cases:
pages directory, you can specify a localized URL segment (part of a URL in between / or at the end of the path) using the slug key identifier. More details on how to do this below.useMessages hook. Imagine CSS but for localizable strings.To summarize:
Creating and managing those files is as simple as creating a style sheet, but here are the important details:
.properties files. Yes, you might wonder why, but there are good reasons documented in the design decision document.UTF-8. Not doing so will replace non-Latin characters with �..properties files, we follow a strict naming convention: <PageFilename>.<locale>.properties<applicationId>.<context>.<id> where:
next-multilingual/configaboutUsPage or footerComponent could be good examples of context. Each file can only contain 1 context and context should not be used across many files as this could cause "key collision" (non-unique keys).. and can only contain between 1 to 50 alphanumeric characters - we recommend using camel case for readability.slug identifier.title identifier.getTitle API provided in next-multilingual/messages to automatically fallback between the title and slug keys.useMessages hook.Also, make sure to check your console log for warnings about potential issues with your messages. It can be tricky to get used to how it works first, but we tried to make it easy to detect and fix problems. Note that those logs will only show in non-production environments.
It's not uncommon to need localized messages while being unable to use hooks. An example would be while using one of Next.js' core features is its builtin API support. In that context, instead of using useMessage we can simply use getMessages while specifying the locale argument.
As mentioned previously, there is one special key for pages, where the id is slug. Unlike traditional slugs that look like this-is-a-page, we ask you to write the slug as a normal and human readable sentence, so that it can be translated like any other string. This avoids having special processes for slugs which can be costly and complex to manage in multiple languages.
Basically, the slug is the human readable "short description" of your page, and represents a segment (part between / or at the end of the path) of a URL. When used as a URL segment, the following transformation is applied:
-For example, About Us will become about-us.
For the homepage, the URL will always be / which means that slug keys will not be used to create localized URL segments.
Don't forget, slugs must be written as a normal short description, which means skipping words to keep it shorter for SEO is discouraged. The main reason for this, is that if you write "a bunch of keywords", a linguist who is not familiar with SEO might have a hard time translating that message. Having SEO specialists in many languages would also be very costly and difficult to scale. In an ideal scenario, market-specific SEO pages should probably be authored and optimized in the native languages, but this is no longer part of the translation process. next-multilingual's focus is to provide an easy, streamlined solution to localize URLs in many languages.
The slug key will also be used as a fallback of the title key when using the getTitle API provided in next-multilingual/messages. This API makes it easy to customize titles when a slug feels insufficient.
⚠️ Note that changing a
slugvalue means that a URL will change. Since those changes are happening innext.config.js, like any Next.js config change, the server must be restarted to see the changes in effect. The same applies if you change the folder structure since the underlying configuration relies on this.
If you want to have a directory without any pages, you can still localize it by creating an index.<locale>.properties file (where locale are the locales you support). While this option is supported, we don't recommend using it as this will make URL paths longer which goes against SEO best practice.
By default, next-multilingual will exclude some files like custom error pages, or any API routes under the /api directory. You can always use slug keys when using messages for these files, but they will not be used to create localized URLs.
You can always look into the example to see message files in action, but here is a sample that could be used on the homepage:
# Homepage title
exampleApp.homepage.title = Homepage
# Homepage headline
exampleApp.homepage.headline = Welcome to the homepage
Now that we learned how to create the homepage and some of the details around how things work, we can easily create other pages. We create many pages in the example, but here is a sample of what about-us.jsx could look like:
import { NextPage } from 'next'
import { getTitle, useMessages } from 'next-multilingual/messages'
import Layout from '@/layout'
import styles from './index.module.css'
const AboutUs: NextPage = () => {
const messages = useMessages()
const title = getTitle(messages)
return (
<Layout title={title}>
<h1 className={styles.headline}>{title}</h1>
<p>{messages.format('details')}</p>
</Layout>
)
}
export default AboutUs
And of course you would have this message file about-us.en-US.properties:
# Page localized URL segment (slug) in (translatable) human readable format.
# This key will be "slugified" (e.g, "About Us" will become "about-us"). All non-alphanumeric characters will be replaced by "-".
exampleApp.aboutUsPage.slug = About Us
# Page details.
exampleApp.aboutUsPage.details = This is just some english boilerplate text.
next-multilingual comes with its own <Link> component that allows for client side and server side rendering of localized URL. It's usage is simple, it works exactly like Next.js' <Link>.
The only important thing to remember is that the href attribute should always contain the Next.js URL. Meaning, the file structure under the pages folder should be what is used and not the localized versions.
In other words, the file structure is considered as the "non-localized" URL representation, and <Link> will take care of replacing the URLs with the localized versions (from the messages files), if they differ from the structure.
The API is available under next-multilingual/link and you can use it like this:
import Link from 'next-multilingual/link'
import { useMessages } from 'next-multilingual/messages'
const Menu: React.FC = () => {
const messages = useMessages()
return (
<nav>
<Link href="/">
<a>{messages.format('home')}</a>
</Link>
<Link href="/about-us">
<a>{messages.format('aboutUs')}</a>
</Link>
<Link href="/contact-us">
<a>{messages.format('contactUs')}</a>
</Link>
</nav>
)
}
export default Menu
Each of these links will be automatically localized when the slug key is specified in that page's message file. For example, in U.S. English the "Contact Us" URL path will be /en-us/contact-us while in Canadian French it will be /fr-ca/nous-joindre.
As the data for this mapping is not immediately available during rendering, next-multilingual/link/ssr will take care of the server side rendering (SSR). By using next-multilingual/config's getConfig, the Webpack configuration will be added automatically. If you are using the advanced Config method, this explains why the special Webpack configuration is required in the example provided prior.
Not all localized URLs are using the <Link> component and this is also why Next.js has the router.push method that can be used by many other use cases. next-multilingual can support these use cases with the useLocalizedUrl hook that will return a localized URL, usable by any components. Here is an example on how it can be leveraged:
import { NextPage } from 'next'
import { useMessages } from 'next-multilingual/messages'
import { useLocalizedUrl } from 'next-multilingual/url'
import router from 'next/router'
const Tests: NextPage = () => {
const messages = useMessages()
const localizedUrl = useLocalizedUrl('/about-us')
return <button onClick={() => router.push(localizedUrl)}>{messages.format('clickMe')}</button>
}
export default Tests
If you prefer to define your URLs inline instead than at the top of the component, or if you need to do more advanced URL manipulations, you can also use the useGetLocalizedUrl hook that returns a function to get URLs:
import { NextPage } from 'next'
import { useMessages } from 'next-multilingual/messages'
import { useGetLocalizedUrl } from 'next-multilingual/url'
import router from 'next/router'
const Tests: NextPage = () => {
const messages = useMessages()
const { getLocalizedUrl } = useGetLocalizedUrl()
return (
<button onClick={() => router.push(getLocalizedUrl('/about-us'))}>
{messages.format('clickMe')}
</button>
)
}
export default Tests
⚠ Be careful, if you want to use the string value of the URL inside React elements, you will have errors because the URLs differ between pre-rendering and the browser. The reason for this is that on the client, on first render, Next.js doesn't have access to the rewrites data, and therefore uses "semi-localized" URL paths (e.g.
/fr-ca/about-us). Since this is a native Next.js behavior, the simplest way to work around this for now is by addingsuppressHydrationWarning={true}to your element. To work around this,useGetLocalizedUrlalso returns aisLoadingproperty that can be used to track when the localized URLs are available to use on the client.
You might run into situation where you also need to get a localized URL but using a hook is not an option. This is where getLocalizedUrl in next-multilingual/url comes in. It acts the same as useLocalizedUrl but its locale argument is mandatory.
Imagine using Next.js' API to send transactional emails and wanting to leverage next-multilingual's localized URLs without having to hardcode them in a configuration. Here is an example of how it can be used:
import type { NextApiRequest, NextApiResponse } from 'next'
import { isLocale } from 'next-multilingual'
import { getMessages } from 'next-multilingual/messages'
import { getLocalizedUrl } from 'next-multilingual/url'
import { sendEmail } from 'send-email'
/**
* The "/api/send-email" handler.
*/
const handler = (request: NextApiRequest, response: NextApiResponse): Promise<void> => {
const locale = request.headers['accept-language']
let emailAddress = ''
try {
emailAddress = JSON.parse(request.body).emailAddress
} catch (error) {
response.status(400)
return
}
if (locale === undefined || !isLocale(locale) || !emailAddress.length) {
response.status(400)
return
}
const messages = getMessages(locale)
sendEmail(
emailAddress,
messages.format('welcome', { loginUrl: await getLocalizedUrl('/login', locale, true) })
)
response.status(200)
}
export default handler
Creating components is the same as pages but they live outside the pages directory. Also, the slug key (if used) will not have any impact on URLs. We have a few example components that should be self-explanatory but here is an example of a Footer.tsx component:
import { useMessages } from 'next-multilingual/messages'
const Footer: React.FC = () => {
const messages = useMessages()
return <footer>{messages.format('footerMessage')}</footer>
}
export default Footer
And its messages file:
# This is the message in the footer at the bottom of pages
exampleApp.footerComponent.footerMessage = © Footer
Also make sure to look at the language switcher component example that is a must in all multilingual applications.
We've been clear that sharing messages is a bad practice from the beginning, so what are we talking about here? In fact, sharing messages by itself is not bad. What can cause problems is when you share messages in different contexts. For example, you might be tempted to create a Button.ts shared message file containing yesButton, noButton keys - but this would be wrong. In many languages simple words such as "yes" and "no" can have different spellings depending on the context, even if it's a button.
When is it good to share messages? For lists of items.
For example, to keep your localization process simple, you want to avoid storing localizable strings in your database (more details on why in the design decision document). In your database you would identify the context using unique identifiers and you would store your messages in shared message files, where your key's identifiers would match the ones from the database.
To illustrate this we created one example using fruits. All you need to do, is create a hook that calls useMessages like this:
export { useMessages as useFruitsMessages } from 'next-multilingual/messages'
❗ If you need to access your messages outside of hooks, you need to also export
getMessages.
Of course, you will have your messages files in the same directory:
exampleApp.fruits.banana = Banana
exampleApp.fruits.apple = Apple
exampleApp.fruits.strawberry = Strawberry
exampleApp.fruits.grape = Grape
exampleApp.fruits.orange = Orange
exampleApp.fruits.watermelon = Watermelon
exampleApp.fruits.blueberry = Blueberry
exampleApp.fruits.lemon = Lemon
And to use it, simple import this hook from anywhere you might need these values:
import { useFruitsMessages } from '../messages/useFruitsMessages'
const FruitList: React.FC () => {
const fruitsMessages = useFruitsMessages()
return (
<>
{fruitsMessages
.getAll()
.map((message) => message.format())
.join(', ')}
</>
)
}
export default FruitList
You can also call individual messages like this:
fruitsMessages.format('banana')
The idea to share those lists of items is that you can have a consistent experience across different components. Imagine a dropdown with a list of fruits in one page, and in another page an auto-complete input. But the important part to remember is that the list must always be used in the same context, not to re-use some of the messages in a different context.
Using placeholders in messages is a critical functionality as not all messages contain static text. next-multilingual supports the ICU MessageFormat syntax out of the box which means that you can use the following message:
exampleApp.homepage.welcome = Hello {name}!
And inject back the values using:
messages.format('welcome', { name: 'John Doe' })
formatThere are a few simple rules to keep in mind when using format:
values argument when formatting the message, it will simply output the message as static text.values argument when formatting the message, you must include the values of all placeholders using the {placeholder} syntax in your message. Otherwise the message will not be displayed.values that are not in your message, they will be silently ignored.One of the main benefits of ICU MessageFormat is to use Unicode's tools and standards to enable applications to sound fluent in most languages. A lot of engineers might believe that by having 2 messages, one for singular and one for plural is enough to stay fluent in all languages. In fact, Unicode documented the plural rules of over 200 languages and some languages like Arabic can have up to 6 plural forms.
To ensure that your sentence will stay fluent in all languages, you can use the following message:
exampleApp.homepage.mfPlural = {count, plural, =0 {No candy left.} one {Got # candy left.} other {Got # candies left.}}
And the correct plural form will be picked, using the correct plural categories defined by Unicode:
messages.format('mfPlural', { count })
There is a lot to learn on this topic. Make sure to read the Unicode documentation and try the syntax yourself to get more familiar with this under-hyped i18n capability.
In a rare event where you would need to use both placeholders using the {placeholder} syntax and also display the { and } characters in a message, you will need to replace them by the { (for {) and } (for }) HTML entities which are recognized by translation tools like this:
exampleApp.debuggingPage.variableInfo = Your variable contains the following values: {{values}}
If you have a message without values (placeholders), escaping { and } with HTML entities is not required and will display entities as static text.
It is a very common situation that we need to have inline HTML, inside a single message. One way to do this would be:
# Bad example, do not ever do this!
exampleApp.homepage.createAccount1 = Please
exampleApp.homepage.createAccount2 = create your account
exampleApp.homepage.createAccount3 = today for free.
And then:
<div>
{messages.format('createAccount1')}
<Link href="/sign-up">{messages.format('createAccount2')}</Link>
{messages.format('createAccount3')}
</div>
There are 2 problems with this approach:
This is actually an anti-pattern called concatenation and should always be avoided. This is the correct way to do this, using formatJsx:
exampleApp.homepage.createAccount = Please <link>create your account</link> today for free.
And then:
<div>{messages.formatJsx('createAccount', { link: <Link href="/sign-up"></Link> })}</div>
formatJsxformatJsx support both placeholders and JSX elements as values which means that you can benefit from the standard format features (e.g., plurals) while injecting JSX elements.
There are a few simple rules to keep in mind when using format:
formatJsx.<link> XML tag, the JSX element needs to be provided using link: <Link href="/"></Link>.<i> many times in a sentence, you will need to create unique tags like <i1>, <i2>, etc. and pass their values in argument as JSX elements.Hello <name>{name}</name>) is not supported..properties file.<Link href="/contact-us><a id="test"></a></Link> is valid but <div><span1></span1><span2></span2></div> is invalid. Instead you must use same-level XML markup in the .properties file and not as a JSX argument.< and >When using formatJsx you will still need to escape curly brackets if you want to display them as text. Additionally, since we will be using XML in the formatJsx messages, similar rules will apply to < and > which are used to identify tags.
In a rare event where you would need to inject JSX in a message using the <element></element> (XML) syntax and also display the < and > characters in a message, you will need to replace them by the < (for <) and > (for >) HTML entities which are recognized by translation tools like this:
exampleApp.statsPage.targetAchieved = You achieved your weekly target (<5) and are eligible for a <link>reward</link>.
Anchor links are links that takes you to a particular place in a document rather than the top of it.
One of next-multilingual's core feature is supporting localized URLs. Our design has been built using normal sentences that are easy to localize and then transformed into SEO-friendly slugs. We can use the same function to slugify anchor links, so that instead of having /fr-ca/nous-joindre#our-team you can have /fr-ca/nous-joindre#notre-équipe.
There are two type of anchor links:
If the anchor links are on the same page, and not referred on any other pages, you can simply add them in the .properties file associate with that page like this:
# Table of content header
exampleApp.longPage.tableOfContent = Table of Content
# This key will be used both as content and "slugified". Make sure when translating that its value is unique.
exampleApp.longPage.p1Header = Paragraph 1
# "Lorem ipsum" text to make the (long) page scroll
exampleApp.longPage.p1 = Lorem ipsum dolor sit amet...
And then the page can use the slugify function to link to to the unique identifier associated with the element you want to point the URL fragment to:
import { NextPage } from 'next'
import Link from 'next-multilingual/link'
import { slugify, useMessages } from 'next-multilingual/messages'
import { useRouter } from 'next/router'
const LongPage: NextPage = () => {
const messages = useMessages()
const { locale } = useRouter()
return (
<div>
<div>
<h2>{messages.format('tableOfContent')}</h2>
<ul>
<li>
<Link href={`#${slugify(messages.format('p1Header'), locale)}`}>
{messages.format('p1Header')}
</Link>
</li>
</ul>
</div>
<div>
<h2 id={slugify(messages.format('p1Header'), locale)}>{messages.format('p1Header')}</h2>
<p>{messages.format('p1')}</p>
</div>
</div>
)
}
export default LongPage
It's also common to use anchor links across pages, so that when you click a link, your browser will directly show the relevant content on that page. To do this, you need to make your page's message available to other pages by adding this simple export that will act just like "shared messages":
export const useLongPageMessages = useMessages
And then you can use this hook from another page like this:
import { NextPage } from 'next'
import Link from 'next-multilingual/link'
import { slugify, useMessages } from 'next-multilingual/messages'
import { useRouter } from 'next/router'
import { useLongPageMessages } from './long-page'
const AnchorLinks: NextPage = () => {
const messages = useMessages()
const { locale, pathname } = useRouter()
const longPageMessages = useLongPageMessages()
return (
<div>
<div>
<Link
href={`${pathname}/long-page#${slugify(longPageMessages.format('p3Header'), locale)}`}
>
{messages.format('linkAction')}
</Link>
</div>
</div>
)
}
export default AnchorLinks
This pattern also works for components. The benefit of doing this is that if you delete, or refactor the page, the anchor links associated with it will always stay with the page.
You could create a separate shared message component just for the anchor links but this would break the proximity principle.
A full example of anchor links can be found in the example application.
One feature that is missing from Next.js is managing important HTML tags used for SEO. We added the <Head> component to deal with two very important tags that live in the HTML <head>:
<link rel=canonical>): this tells search engines that the source of truth for the page being browsed is this URL. Very important to avoid being penalized for duplicate content, especially since URLs are case insensitive, but Google treats them as case-sensitive.<link rel=alternate>): this tells search engines that the page being browsed is also available in other languages and facilitates crawling of the site.The API is available under next-multilingual/head and you can import it like this:
import Head from 'next-multilingual/head'
Just like <Link>, <Head> is meant to be a drop-in replacement for Next.js' <Head> component. In our example, we are using it in the Layout component, like this:
<Head>
<title>{title}</title>
<meta name="viewport" content="width=device-width, initial-scale=1.0"></meta>
</Head>
All this does is insert the canonical and alternate links so that search engines can better crawl your application. For example, if you are on the /en-us/about-us page, the following HTML will be added automatically under your HTML <head> tag:
<link rel="canonical" href="http://localhost:3000/en-us/about-us" />
<link rel="alternate" href="http://localhost:3000/en-us/about-us" hreflang="en-US" />
<link rel="alternate" href="http://localhost:3000/fr-ca/%C3%A0-propos-de-nous" hreflang="fr-CA" />
To fully benefit from the SEO markup, <Head> must be included on all pages. There are multiple ways to achieve this, but in the example, we created a <Layout> component that is used on all pages.
Like most sites, you will want to leverage Next.js' custom error pages capability. With useMessages(), it's just as easy as creating any other pages. For example, for a 404 error, you can create your 404.tsx:
import { NextPage } from 'next'
import Link from 'next-multilingual/link'
import { getTitle, useMessages } from 'next-multilingual/messages'
import Layout from '@/layout'
const Error404: NextPage = () => {
const messages = useMessages()
const title = getTitle(messages)
return (
<Layout title={title}>
<h1>{title}</h1>
<Link href="/">
<a>{messages.format('goBack')}</a>
</Link>
</Layout>
)
}
export default Error404
And of course, your messages, for example 404.en-US.properties:
# Page title
exampleApp.pageNotFoundError.title = 404 - Page Not Found
# Go back link text
exampleApp.pageNotFoundError.goBack = Go back home
APIs often need to be localized. Here is an "Hello API" example:
import type { NextApiRequest, NextApiResponse } from 'next'
import { getMessages } from 'next-multilingual/messages'
/**
* Example API schema.
*/
type Schema = {
message: string
}
/**
* The "hello API" handler.
*/
const handler = (request: NextApiRequest, response: NextApiResponse<Schema>): void => {
const locale = request.headers['accept-language']
if (locale === undefined || !isLocale(locale)) {
response.status(400)
return
}
const messages = getMessages(locale)
response.status(200).json({ message: messages.format('message') })
}
This is very similar to the API implemented in the example application. We are using the Accept-Language HTTP header to tell the API in which locale we want its response to be. Unlike the useMessages hook that has the context of the current locale, we need to tell getMessages in which locale to return messages.
Message files behave exactly the same as with useMessages You simply need to create one next to the API Route's file, in our case hello.en-US.properties:
# API message
exampleApp.helloApi.message = Hello, from API.
You can implement this in any pages, just like any other React-based API call, like this:
const SomePage: NextPage = () => {
const [apiError, setApiError] = useState(null)
const [isApiLoaded, setApiIsLoaded] = useState(false)
const [apiMessage, setApiMessage] = useState('')
useEffect(() => {
setApiIsLoaded(false)
const requestHeaders: HeadersInit = new Headers()
requestHeaders.set('Accept-Language', normalizeLocale(router.locale as string))
fetch('/api/hello', { headers: requestHeaders })
.then((result) => result.json())
.then(
(result) => {
setApiIsLoaded(true)
setApiMessage(result.message)
},
(apiError) => {
setApiIsLoaded(true)
setApiError(apiError)
}
)
}, [router.locale])
const showApiMessage: React.FC = () => {
if (apiError) {
return (
<>
{messages.format('apiError')}
{(apiError as Error).message}
</>
)
} else if (!isApiLoaded) {
return <>{messages.format('apiLoading')}</>
} else {
return <>{apiMessage}</>
}
}
return (
<div>
<h2>{messages.format('apiHeader')}</h2>
<div>{showApiMessage({})}</div>
</div>
)
}
The normalizeLocale is not mandatory but a recommended ISO 3166 convention. Since Next.js uses the locales as URL prefixes, they are lower-cased in the configuration and can be re-normalized as needed.
❗ Dynamic routes are complex and localizing them adds even more complexity. Make sure you are familiar with how this Next.js feature works before trying to add localization.
Dynamic routes are very common and supported out of the box by Next.js. Since version 3.0, next-multilingual provides the same supports as Next.js in terms of dynamic routes. To make dynamic routes work with next-multilingual we have a few patterns to follow:
<Link>'s href attribute and the useLocalizedUrl/useGetLocalizedUrl/getLocalizedUrl url argument only accept string URLs.
<Link> component which accepts a UrlObject, we preferred to streamline our types since urlObject.href can easily be used instead.userRouter().asPath (most common scenario) by providing localized parameters directly in the URL. By using asPath you are using the localized URL which means that the URL you will use will be fully localized.userRouter().pathname is conjunction with hydrateRouteParameters by providing localized parameters. By using pathname you are using the non-localized URL which means that the URL you will use might be a mix of non-localized segments plus the localized parameters. This can be useful in cases where you have nested dynamic routes.We provided several examples of on on to use dynamic routes in our dynamic route test pages.
The main challenge with dynamic routes, is that if the value of the parameter needs to be localized, we need to keep a relation between languages so that we can correctly switch languages. next-multilingual solves this problem with its getLocalizedRouteParameters API that creates a LocalizedRouteParameters object used as a page props. This can work both with getStaticProps and getServerSideProps.
getStaticPropsFirst you need to tell Next.js which predefined paths will be valid by using getStaticPaths (all imports are added in the first example):
import { getCitiesMessages } from '@/messages/cities/citiesMessages'
import { GetStaticPaths } from 'next'
import { slugify } from 'next-multilingual/messages'
export const getStaticPaths: GetStaticPaths = async (context) => {
const paths: MultilingualStaticPath[] = []
const { locales } = getStaticPathsLocales(context)
locales.forEach((locale) => {
const citiesMessages = getCitiesMessages(locale)
citiesMessages.getAll().forEach((cityMessage) => {
paths.push({
params: {
city: slugify(cityMessage.format(), locale),
},
locale,
})
})
})
return {
paths,
fallback: false,
}
}
Then you have to pre-compute the localized route parameters and return them as props using getStaticProps and getLocalizedRouteParameters:
export type CityPageProps = { localizedRouteParameters: LocalizedRouteParameters }
export const getStaticProps: GetStaticProps<CityPageProps> = async (context) => {
const localizedRouteParameters = getLocalizedRouteParameters(
context,
{
city: getCitiesMessages,
},
import.meta.url
)
return { props: { localizedRouteParameters } }
}
If you are using a catch-all dynamic route, you will need to pass your parameters as an array, for each URL segment that you want to support. For example, if you want to support 2 levels:
const localizedRouteParameters = getLocalizedRouteParameters(context, {
city: [getCitiesMessages, getCitiesMessages],
})
Note that since we need to use the getMessages API instead of the useMessages hook, you will also need to export it in the message file:
export {
getMessages as getCitiesMessages,
useMessages as useCitiesMessages,
} from 'next-multilingual/messages'
Finally you have to pass down your localized route parameters down to your language switcher component when you create your page:
const CityPage: NextPage<CityPageProps> = ({ localizedRouteParameters }) => {
const messages = useMessages()
const title = getTitle(messages)
const { query } = useRouter()
return (
<Layout title={title} localizedRouteParameters={localizedRouteParameters}>
<h1>{query['city']}</h1>
</Layout>
)
}
export default CityPage
The only part missing now is the language switcher which needs to leverage the localized route parameters by using getLanguageSwitcherUrl:
import { normalizeLocale, setCookieLocale } from 'next-multilingual'
import Link from 'next-multilingual/link'
import { KeyValueObject } from 'next-multilingual/messages'
import { LocalizedRouteParameters, useRouter } from 'next-multilingual/router'
import { getLanguageSwitcherUrl } from 'next-multilingual/url'
import { ReactElement } from 'react'
// Locales don't need to be localized.
const localeStrings: KeyValueObject = {
'en-US': 'English (United States)',
'fr-CA': 'Français (Canada)',
}
type LanguageSwitcherProps = {
/** Route parameters, if the page is using a dynamic route. */
localizedRouteParameters?: LocalizedRouteParameters
}
export const LanguageSwitcher: React.FC<LanguageSwitcherProps> = ({ localizedRouteParameters }) => {
const router = useRouter()
const { pathname, locale: currentLocale, locales, defaultLocale, query } = useRouter()
const href = getLanguageSwitcherUrl(router, localizedRouteParameters)
return (
<div id="language-switcher">
<ul>
{locales
.filter((locale) => locale !== currentLocale)
.map((locale) => {
return (
<li key={locale}>
<Link href={href} locale={locale}>
<a
onClick={() => {
setCookieLocale(locale)
}}
lang={normalizeLocale(locale)}
>
{localeStrings[normalizeLocale(locale)]}
</a>
</Link>
</li>
)
})}
</ul>
</div>
)
}
Check out our fully working examples:
Our ideal translation process is one where you send the modified files to your localization vendor (while working in a branch), and get back the translated files, with the correct locale in the filenames. Once you get the files back you basically submit them back in your branch which means localization becomes an integral part of the development process. Basically, the idea is:
We don't have any "export/import" tool to help as at the time of writing this document.
next-multilingual? 🗳️Why did we put so much effort into these details? Because our hypothesis is that it can have a major impact on:
More details can be found on the implementation and design decision in the individual README files of each API and in the documentation directory.
FAQs
An opinionated end-to-end solution for Next.js applications that requires multiple languages.
The npm package next-multilingual receives a total of 19 weekly downloads. As such, next-multilingual popularity was classified as not popular.
We found that next-multilingual demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 0 open source maintainers collaborating on the project.
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