Routing
Routing APIs are only needed when you’re using i18n routing.
next-intl
integrates with the routing system of Next.js in two places:
- Middleware: Negotiates the locale and handles redirects & rewrites (e.g.
/
→/en
) - Navigation APIs: Lightweight wrappers around Next.js’ navigation APIs like
<Link />
This enables you to express your app in terms of APIs like <Link href="/about">
, while aspects like the locale and user-facing pathnames are automatically handled behind the scenes (e.g. /de/ueber-uns
).
defineRouting
The routing configuration that is shared between the middleware and the navigation APIs can be defined with the defineRouting
function.
import {defineRouting} from 'next-intl/routing';
export const routing = defineRouting({
// A list of all locales that are supported
locales: ['en', 'de'],
// Used when no locale matches
defaultLocale: 'en'
});
Depending on your routing needs, you may wish to consider further settings—see below.
What if the locales aren’t known at build time?
In case you’re building an app where locales can be added and removed at runtime, you can provide the routing configuration for the middleware dynamically per request.
To create the corresponding navigation APIs, you can omit the locales
argument from createNavigation
in this case.
Still, in case you’re defining other routing config, make sure to keep them in sync between the middleware and the navigation APIs.
localePrefix
By default, the pathnames of your app will be available under a prefix that matches your directory structure (e.g. /en/about
→ app/[locale]/about/page.tsx
). You can however adapt the routing to optionally remove the prefix or customize it per locale by configuring the localePrefix
setting.
localePrefix: 'always'
(default)
By default, pathnames always start with the locale (e.g. /en/about
).
import {defineRouting} from 'next-intl/routing';
export const routing = defineRouting({
// ...
localePrefix: 'always'
});
localePrefix: 'as-needed'
If you want to use no prefix for the default locale (e.g. /about
) while keeping it for other locales (e.g. /de/about
), you can configure your routing accordingly:
import {defineRouting} from 'next-intl/routing';
export const routing = defineRouting({
// ...
localePrefix: 'as-needed'
});
Note that:
- If you use this routing strategy, make sure that your middleware matcher detects unprefixed pathnames.
- The middleware will by default set a cookie to remember the user’s locale preference. If no explicit locale prefix is present in the pathname, then locale detection will potentially redirect users to the latest locale that was matched based on the cookie value (e.g.
/
→/de
). - If a superfluous locale prefix like
/en/about
is requested, the middleware will automatically redirect to the unprefixed version/about
. This can be helpful in case you’re redirecting from another locale and you want to update a potential cookie value first (e.g.<Link />
relies on this mechanism).
localePrefix: 'never'
If you’d like to provide a locale to next-intl
, e.g. based on user settings, you can consider setting up next-intl
without i18n routing. This way, you don’t need to use the routing integration in the first place.
However, you can also configure the middleware to never show a locale prefix in the URL, which can be helpful in the following cases:
- You want to use domain-based routing and have only one locale per domain
- You want to use a cookie to determine the locale while enabling static rendering
import {defineRouting} from 'next-intl/routing';
export const routing = defineRouting({
// ...
localePrefix: 'never'
});
In this case, requests for all locales will be rewritten to have the locale only prefixed internally. You still need to place all your pages inside a [locale]
folder for the routes to be able to receive the locale
param.
Note that:
- If you use this routing strategy, make sure that your middleware matcher detects unprefixed pathnames.
- Alternate links are disabled in this mode since URLs might not be unique per locale. Due to this, consider including these yourself, or set up a sitemap that links localized pages via
alternates
. - You can consider increasing the
maxAge
attribute of the locale cookie to a longer duration to remember the user’s preference across sessions.
prefixes
If you’d like to customize the user-facing prefix, you can provide a locale-based mapping:
import {defineRouting} from 'next-intl/routing';
export const routing = defineRouting({
locales: ['en-US', 'de-AT', 'zh'],
defaultLocale: 'en-US',
localePrefix: {
mode: 'always',
prefixes: {
'en-US': '/us',
'de-AT': '/eu/at'
// (/zh will be used as-is)
}
}
});
Note that:
- You should adapt your middleware matcher to match the custom prefixes.
- Custom prefixes are only visible to the user and rewritten internally to the corresponding locale. Therefore, the
[locale]
segment corresponds to the locale, not the prefix.
Can I read the matched prefix in my app?
Since the custom prefix is rewritten to the locale internally, you can’t access the prefix directly. However, you can extract details like the region from the locale:
import {useLocale} from 'next-intl';
function Component() {
// Assuming the locale is 'en-US'
const locale = useLocale();
// Extracts the "US" region
const {region} = new Intl.Locale(locale);
}
The region must be a valid ISO 3166-1 alpha-2 country code or a UN M49 region code. When passed to Intl.Locale
, the region code is treated as case-insensitive and normalized to uppercase. You can also combine languages with regions where the language is not natively spoken (e.g. en-AT
describes English as used in Austria).
Apart from the region, a locale can encode further properties, like the numbering system.
If you’d like to encode custom information in the locale, you can use arbitrary private extensions, denoted by the -x-
prefix (e.g. en-US-x-usd
). The Intl.Locale
constructor ignores private extensions, but you can extract them from the locale string manually.
pathnames
Many apps choose to localize pathnames, especially when search engine optimization is relevant.
Example:
/en/about
/de/ueber-uns
Since you typically want to define these routes only once internally, you can use the next-intl
middleware to rewrite such incoming requests to shared pathnames.
import {defineRouting} from 'next-intl/routing';
export const routing = defineRouting({
locales: ['en-US', 'en-UK', 'de'],
defaultLocale: 'en-US',
// The `pathnames` object holds pairs of internal and
// external paths. Based on the locale, the external
// paths are rewritten to the shared, internal ones.
pathnames: {
// If all locales use the same pathname, a single
// external path can be used for all locales
'/': '/',
'/blog': '/blog',
// If some locales use different paths, you can
// specify the relevant external pathnames
'/about': {
de: '/ueber-uns'
},
// Dynamic params are supported via square brackets
'/news/[articleSlug]': {
de: '/neuigkeiten/[articleSlug]'
},
// Static pathnames that overlap with dynamic segments
// will be prioritized over the dynamic segment
'/news/just-in': {
de: '/neuigkeiten/aktuell'
},
// Also (optional) catch-all segments are supported
'/categories/[...slug]': {
de: '/kategorien/[...slug]'
}
}
});
Localized pathnames map to a single internal pathname that is created via the file-system based routing in Next.js. In the example above, /de/ueber-uns
will be handled by the page at /[locale]/about/page.tsx
.
How can I revalidate localized pathnames?
Depending on if a route is generated statically (at build time) or dynamically (at runtime), revalidatePath
needs to be called either for the localized or the internal pathname.
Consider this example:
app
└── [locale]
└── news
└── [slug]
… with this routing configuration:
import {defineRouting} from 'next-intl/routing';
export const routing = defineRouting({
locales: ['en', 'de'],
defaultLocale: 'en',
pathnames: {
'/news/[slug]': {
en: '/news/[slug]',
de: '/neuigkeiten/[slug]'
}
}
});
Depending on whether some-article
was included in generateStaticParams
or not, you can revalidate the route like this:
// Statically generated at build time
revalidatePath('/de/news/some-article');
// Dynamically generated at runtime:
revalidatePath('/de/neuigkeiten/some-article');
When in doubt, you can revalidate with revalidateTag
instead.
See also: vercel/next.js#59825
How can I localize dynamic segments?
If you have a route like /news/[articleSlug]-[articleId]
, you may want to localize the articleSlug
part in the pathname like this:
/en/news/launch-of-new-product-94812
/de/neuigkeiten/produktneuheit-94812
In this case, the localized slug can either be provided by the backend or generated in the frontend by slugifying the localized article title.
A good practice is to include the ID in the URL, allowing you to retrieve the article based on this information from the backend. The ID can be further used to implement self-healing URLs, where a redirect is added if the articleSlug
doesn’t match.
If you localize the values for dynamic segments, you might want to turn off alternate links and provide your own implementation that considers localized values for dynamic segments.
How do I integrate with an external system like a CMS that provides localized pathnames?
In case you’re using a system like a CMS to configure localized pathnames, you’ll typically implement this with a dynamic segment that catches all localized pathnames instead of using the pathnames
configuration from next-intl
.
Examples:
- All pathnames are handled by your CMS:
[locale]/[[...slug]]/page.tsx
- Some pathnames are handled by your CMS:
[locale]/blog/[...slug]/page.tsx
import {notFound} from 'next';
import {Locale} from 'next-intl';
import {fetchContent} from './cms';
type Props = {
params: Promise<{
locale: Locale;
slug: Array<string>;
}>;
};
export default async function CatchAllPage({params}: Props) {
const {locale, slug} = await params;
const content = await fetchContent(locale, slug);
if (!content) notFound();
// ...
}
In this case, you’ll likely want to disable alternate links and provide your own implementation instead.
Furthermore, in case you provide a locale switcher, it might require special care to be able to switch between localized pathnames of the same page. A simplified implementation might always redirect to the home page instead.
domains
If you want to serve your localized content based on different domains, you can provide a list of mappings between domains and locales via the domains
setting.
Examples:
us.example.com
:en-US
ca.example.com
:en-CA
ca.example.com/fr
:fr-CA
fr.example.com
:fr-FR
In many cases, domains
are combined with a localePrefix
setting to achieve results as shown above. Also custom prefixes can be used to customize the user-facing prefix per locale.
import {defineRouting} from 'next-intl/routing';
export const routing = defineRouting({
locales: ['en-US', 'en-CA', 'fr-CA', 'fr-FR'],
defaultLocale: 'en-US',
domains: [
{
domain: 'us.example.com',
defaultLocale: 'en-US',
locales: ['en-US']
},
{
domain: 'ca.example.com',
defaultLocale: 'en-CA',
locales: ['en-CA', 'fr-CA']
},
{
domain: 'fr.example.com',
defaultLocale: 'fr-FR',
locales: ['fr-FR']
}
],
localePrefix: {
mode: 'as-needed',
prefixes: {
// Cleaner prefix for `ca.example.com/fr`
'fr-CA': '/fr'
}
}
});
Locales are required to be unique across domains, therefore regional variants are typically used to avoid conflicts. Note however that you don’t necessarily need to provide messages for each locale if the overall language is sufficient for your use case.
If no domain matches, the middleware will fall back to the general defaultLocale
(e.g. on localhost
).
How can I locally test if my setup is working?
To test your domain setup locally, you can conditionally adapt the domains to refer to hosts that are available locally:
import {defineRouting} from 'next-intl/routing';
const isDev = process.env.NODE_ENV === 'development';
export const routing = defineConfig({
// ...
domains: [
{
domain: isDev ? 'localhost:3000' : 'us.example.com'
// ...
},
{
domain: isDev ? 'localhost:3001' : 'ca.example.com'
// ...
}
]
});
Now, you can run your development server on one of the configured ports and test the routing for different use cases:
# Like `us.example.com`
PORT=3000 npm run dev
# Like `ca.example.com`
PORT=3001 npm run dev
Can I use a different localePrefix
setting per domain?
While this is currently not supported out of the box, you can still achieve this by building the app for each domain separately while injecting diverging routing configuration via an environment variable.
Example:
import {defineRouting} from 'next-intl/routing';
const isUsDomain =
process.env.VERCEL_PROJECT_PRODUCTION_URL === 'us.example.com';
export const routing = defineRouting({
locales: isUsDomain ? ['en-US'] : ['en-CA', 'fr-CA'],
defaultLocale: isUsDomain ? 'en-US' : 'en-CA',
localePrefix: isUsDomain ? 'never' : 'always'
});
localeDetection
The middleware will detect a matching locale based on your routing configuration & the incoming request and will either pass the request through for a matching locale or redirect to one that matches.
If you want to rely entirely on the URL to resolve the locale, you can set the localeDetection
property to false
. This will disable locale detection based on the accept-language
header and a potentially existing cookie value from a previous visit.
import {defineRouting} from 'next-intl/routing';
export const routing = defineRouting({
// ...
localeDetection: false
});
In this case, only the locale prefix and a potentially matching domain are used to determine the locale.
localeCookie
If a user changes the locale to a value that doesn’t match the accept-language
header, next-intl
will set a session cookie called NEXT_LOCALE
that contains the most recently detected locale. This is used to remember the user’s locale preference for subsequent requests.
By default, the cookie will be configured with the following attributes:
sameSite
: This value is set tolax
so that the cookie can be set when coming from an external site.path
: This value is not set by default, but will use the value of yourbasePath
if configured.
If you have more specific requirements, you can adjust these settings accordingly:
import {defineRouting} from 'next-intl/routing';
export const routing = defineRouting({
// ...
// Will be merged with the defaults
localeCookie: {
// Custom cookie name
name: 'USER_LOCALE',
// Expire in one year
maxAge: 60 * 60 * 24 * 365
}
});
… or turn the cookie off entirely:
import {defineRouting} from 'next-intl/routing';
export const routing = defineRouting({
// ...
localeCookie: false
});
Which maxAge
value should I consider for GDPR compliance?
The Article 29 Working Party opinion 04/2012 provides a guideline for the expiration of cookies that are used to remember the user’s language in section 3.6 “UI customization cookies”. In this policy, a language preference cookie set as a result of an explicit user action, such as using a language switcher, is allowed to remain active for “a few additional hours” after a browser session has ended.
To be compliant out of the box, next-intl
does not set the max-age
value of the cookie, making it a session cookie that expires when a browser is closed.
Note that this can be beneficial in comparison to an expiration of a few hours since the cookie is guaranteed to remain active while the browser session lasts. On mobile devices, where browsers are infrequently closed but rather suspended to the background, the cookie can remain active even for an extended period.
The Working Party also states that if additional information about the use of cookies is provided in a prominent location (e.g. a “uses cookies” notice next to the language switcher), the cookie can be configured to remember the user’s preference for “a longer duration”. If you’re providing such a notice, you can consider increasing maxAge
accordingly.
Please note that legal requirements may vary by region, so it’s advisable to verify them independently. While we strive to keep this information as up-to-date as possible, we cannot guarantee its accuracy.
alternateLinks
The middleware automatically sets the link
header to inform search engines that your content is available in different languages. Note that this automatically integrates with your routing strategy and will generate the correct links based on your configuration.
However, there are cases where you may want to provide these links yourself:
- You have pages that are only available for certain locales
- You’re using an external system like a CMS to manage localized slugs of your pages
In this case, you can opt-out of this behavior by setting alternateLinks
to false
.
import {defineRouting} from 'next-intl/routing';
export const routing = defineRouting({
// ...
alternateLinks: false
});
If you decide to manage alternate links yourself, a good option can be to include them in a sitemap.
Which alternate links are included?
Using the middleware defaults, the link
header of a response for /
will look like this:
link: <https://example.com/en>; rel="alternate"; hreflang="en",
<https://example.com/de>; rel="alternate"; hreflang="de",
<https://example.com/>; rel="alternate"; hreflang="x-default"
The x-default
entry is included to point to a variant that can be used if no other language matches the user’s browser setting. This special entry is reserved for language selection & detection, in our case issuing a 307 redirect to the best matching locale.
Your middleware configuration, including options like domains
, pathnames
and basePath
, is automatically incorporated.
Can I customize the alternate links?
If you need to customize the alternate links, you can either turn them off and provide your own implementation, or if you only need to make minor adaptions, you can compose the middleware and add your custom logic after the middleware has run:
import createMiddleware from 'next-intl/middleware';
import LinkHeader from 'http-link-header';
import {NextRequest} from 'next/server';
import {routing} from './i18n/routing';
const handleI18nRouting = createMiddleware(routing);
export default async function middleware(request: NextRequest) {
const response = handleI18nRouting(request);
// Example: Remove the `x-default` entry
const link = LinkHeader.parse(response.headers.get('link'));
link.refs = link.refs.filter((entry) => entry.hreflang !== 'x-default');
response.headers.set('link', link.toString());
return response;
}
next.config.ts
Apart from your routing configuration, next-intl
will also incorporate settings from next.config.ts
.
basePath
The next-intl
middleware as well as the navigation APIs will automatically pick up a basePath
that you might have configured in your next.config.js
.
Note however that you should make sure that your middleware matcher
handles the root of your base path:
export const config = {
// The `matcher` is relative to the `basePath`
matcher: [
// This entry handles the root of the base
// path and should always be included
'/'
// ... other matcher config
]
};
trailingSlash
If you have trailingSlash
set to true
in your Next.js config, this setting will be taken into account by the middleware and the navigation APIs.
Note that if you’re using pathnames
, your internal and external pathnames can be defined either with or without a trailing slash as they will be normalized internally.