Creation:2025-03-25Last update:2026-05-06

    Translate your Tanstack Start website with Solid.js using Intlayer | Internationalisation (i18n)

    Table of Contents

    This guide demonstrates how to integrate Intlayer for seamless internationalisation in Tanstack Start projects with Solid.js, locale-aware routing, TypeScript support, and modern development practices.

    What is Intlayer?

    Intlayer is an innovative, open-source internationalisation (i18n) library designed to simplify multi-lingual support in modern web applications.

    With Intlayer, you can:

    • Manage translations easily using declarative dictionaries at the component level.
    • Localise metadata, routes, and content dynamically.
    • Ensure TypeScript support with auto-generated types, improving autocompletion and error detection.
    • Benefit from advanced features, such as dynamic locale detection and switching.
    • Enable locale-aware routing with Tanstack Start's file-based routing system.

    Step-by-Step Guide to Setting Up Intlayer in a Tanstack Start Application

    www.youtube.com

    See the Application Template on GitHub.

    Step 1: Project Creation

    First, create a new TanStack Start project following the Start New Project guide on the TanStack Start website.

    Step 2: Install Intlayer Packages

    Install the necessary packages using your preferred package manager:

    bash
    npm install intlayer solid-intlayernpm install vite-intlayer --save-devnpx intlayer init

    • intlayer

      The core package that provides internationalisation tools for configuration management, translation, content declaration, transpilation, and CLI commands.

    • solid-intlayer The package that integrates Intlayer into the Solid application. It provides context providers and hooks for Solid internationalisation.

    • vite-intlayer Includes the Vite plugin to integrate Intlayer with the Vite bundler, as well as middleware to detect the user's preferred locale, manage cookies, and handle URL redirection.

    Step 3: Configuration of your project

    Create a configuration file to set up the languages of your application:

    intlayer.config.ts
    import type { IntlayerConfig } from "intlayer";import { Locales } from "intlayer";const config: IntlayerConfig = {  internationalization: {    defaultLocale: Locales.ENGLISH,    locales: [Locales.ENGLISH, Locales.FRENCH, Locales.SPANISH],  },};export default config;
    Through this configuration file, you can configure localised URLs, middleware redirection, cookie names, the location and extension of your content declarations, disable Intlayer logs in the console, and more. For a complete list of available parameters, refer to the configuration documentation.

    Step 4: Integrate Intlayer in your Vite Configuration

    Add the intlayer plugin in your configuration:

    vite.config.ts
    import { intlayer } from "vite-intlayer";import { defineConfig } from "vite";import { devtools } from "@tanstack/devtools-vite";import { tanstackStart } from "@tanstack/solid-start/plugin/vite";import solidPlugin from "vite-plugin-solid";export default defineConfig({  plugins: [    devtools(),    tanstackStart({      router: {        routeFileIgnorePattern:          ".content.(ts|tsx|js|mjs|cjs|jsx|json|jsonc|json5)$",      },    }),    solidPlugin({ ssr: true }),    intlayer(),  ],});
    The intlayer() Vite plugin is used to integrate Intlayer with Vite. It ensures the building of content declaration files and monitors them in development mode. It defines the Intlayer environment variables within the Vite application. Additionally, it provides aliases to reduce performance overhead.

    Step 5: Create the Root Layout

    Configure your root layout to support internationalisation by using useParams to detect the current locale and setting the lang and dir attributes on the html tag.

    src/routes/__root.tsx
    import {  HeadContent,  Scripts,  createRootRouteWithContext,} from "@tanstack/solid-router";import { HydrationScript } from "solid-js/web";import { Suspense, type ParentComponent } from "solid-js";import { IntlayerProvider } from "solid-intlayer";import { defaultLocale, getHTMLTextDir } from "intlayer";import { Route as LocaleRoute } from "./{-$locale}/route";export const Route = createRootRouteWithContext()({  shellComponent: RootComponent,});const RootComponent: ParentComponent = (props) => {  const params = LocaleRoute.useParams();  const locale = params()?.locale ?? defaultLocale;  return (    <html dir={getHTMLTextDir(locale)} lang={locale}>      <head>        <HydrationScript />        <HeadContent />      </head>      <body>        <IntlayerProvider locale={locale}>          <Suspense>{props.children}</Suspense>        </IntlayerProvider>        <Scripts />      </body>    </html>  );};

    Step 6: Create the Locale Layout (Optional)

    Create a layout that handles the locale prefix and performs validation. This layout will ensure only valid locales are processed.

    This step is optional if you don't need to validate the locale prefix at the route level.
    src/routes/{-$locale}/route.tsx
    import { createFileRoute, Outlet, redirect } from "@tanstack/solid-router";import { validatePrefix } from "intlayer";export const Route = createFileRoute("/{-$locale}")({  beforeLoad: ({ params }) => {    const localeParam = params.locale;    // Validate the locale prefix    const { isValid, localePrefix } = validatePrefix(localeParam);    if (!isValid) {      throw redirect({        to: "/{-$locale}/404",        params: { locale: localePrefix },        replace: true,      });    }  },  component: Outlet,});
    Here, {-$locale} is a dynamic route parameter that is replaced by the current locale. This notation makes the slot optional, allowing it to work with routing modes like 'prefix-no-default' etc.

    Be aware that this slot may cause issues if you use multiple dynamic segments in the same route (ex: /{-$locale}/other-path/$anotherDynamicPath/...). For 'prefix-all' mode, you might prefer switching the slot to $locale. For 'no-prefix' or 'search-params' mode, you can remove the slot entirely.

    Step 7: Declare Your Content

    Create and manage your content declarations to store translations:

    src/contents/page.content.ts
    import type { Dictionary } from "intlayer";import { t } from "intlayer";const appContent = {  content: {    links: {      about: t({        en: "About",        es: "Acerca de",        fr: "À propos",      }),      home: t({        en: "Home",        es: "Inicio",        fr: "Accueil",      }),    },    meta: {      title: t({        en: "Welcome to Intlayer + TanStack Router",        es: "Bienvenido a Intlayer + TanStack Router",        fr: "Bienvenue à Intlayer + TanStack Router",      }),      description: t({        en: "This is an example of using Intlayer with TanStack Router",        es: "Este es un ejemplo de uso de Intlayer con TanStack Router",        fr: "Ceci est un exemple d'utilisation d'Intlayer avec TanStack Router",      }),    },  },  key: "app",} satisfies Dictionary;export default appContent;
    Your content declarations can be defined anywhere in your application, as long as they are included in the contentDir directory (by default, ./app). And match the content declaration file extension (by default, .content.{json,ts,tsx,js,jsx,mjs,cjs}).
    For more details, refer to the content declaration documentation.

    Step 8: Utilise Locale-Aware Components and Hooks

    Create a LocalizedLink component for locale-aware navigation:

    src/components/LocalizedLink.tsx
    import { Link, type LinkProps } from "@tanstack/solid-router";import { getPrefix } from "intlayer";import { useLocale } from "solid-intlayer";import type { JSX } from "solid-js";export const LOCALE_ROUTE = "{-$locale}" as const;export type RemoveLocaleParam<TVal> = TVal extends string  ? RemoveLocaleFromString<TVal>  : TVal;export type To = RemoveLocaleParam<LinkProps["to"]>;type CollapseDoubleSlashes<TString extends string> =  TString extends `${infer THead}//${infer TTail}`    ? CollapseDoubleSlashes<`${THead}/${TTail}`>    : TString;export type LocalizedLinkProps = Omit<LinkProps, "to"> & {  to?: To;} & JSX.AnchorHTMLAttributes<HTMLAnchorElement>;type RemoveAll<  TString extends string,  TSub extends string,  McPherson,> = TString extends `${infer THead}${TSub}${infer TTail}`  ? RemoveAll<`${THead}${TTail}`, TSub>  : TString;type RemoveLocaleFromString<TString extends string> = CollapseDoubleSlashes<  RemoveAll<TString, typeof LOCALE_ROUTE>>;export const LocalizedLink = (props: LocalizedLinkProps) => {  const { locale } = useLocale();  return (    <Link      {...props}      params={{        locale: getPrefix(locale()).localePrefix,        ...(typeof props.params === "object" ? props.params : {}),      }}      to={`/${LOCALE_ROUTE}${props.to ?? ""}` as LinkProps["to"]}    />  );};

    This component serves two purposes:

    • Removing the unnecessary {-$locale} prefix from the URL.
    • Injecting the locale parameter into the URL to ensure the user is directly redirected to the localised route.

    Then, we can create a useLocalizedNavigate hook for programmatic navigation:

    src/hooks/useLocalizedNavigate.tsx
    import { useNavigate } from "@tanstack/solid-router";import { getLocalizedUrl } from "intlayer";import { useLocale } from "solid-intlayer";export const useLocalizedNavigate = () => {  const navigate = useNavigate();  const { locale } = useLocale();  const localizedNavigate = (to: string) => {    const localizedTo = getLocalizedUrl(to, locale());    return navigate({ to: localizedTo });  };  return localizedNavigate;};

    Step 9: Use Intlayer in Your Pages

    Access your content dictionaries throughout your application:

    Localised Home Page

    src/routes/{-$locale}/index.tsx
    import { createFileRoute } from "@tanstack/solid-router";import { useIntlayer } from "solid-intlayer";import { LocalizedLink } from "@/components/LocalizedLink";export const Route = createFileRoute("/{-$locale}/")({  component: RouteComponent,});function RouteComponent() {  const content = useIntlayer("index-page");  return (    <main>      <h1>{content.heroTitle}</h1>      <p>{content.heroDesc}</p>      <div>        <LocalizedLink to="/">{content.navHome}</LocalizedLink>        <LocalizedLink to="/about">{content.navAbout}</LocalizedLink>      </div>    </main>  );}
    If you want to use your content in a string attribute, such as alt, title, href, aria-label, etc., you can use the value of the function, like:
    html
    <img src="{content.image.src.value}" alt="{content.image.value}" /><img src="{content.image.src.toString()}" alt="{content.image.toString()}" /><img src="{String(content.image.src)}" alt="{String(content.image)}" />

    In Solid, useIntlayer returns reactive content (e.g., content). You can access its properties directly.

    To learn more about the useIntlayer hook, refer to the documentation.

    Step 10: Create a Locale Switcher Component

    Create a component to allow users to change languages:

    src/components/LocaleSwitcher.tsx
    import { useLocation } from "@tanstack/solid-router";import { getLocaleName, getPathWithoutLocale, getPrefix } from "intlayer";import { For } from "solid-js";import { useIntlayer, useLocale } from "solid-intlayer";import { LocalizedLink, type To } from "./LocalizedLink";export const LocaleSwitcher = () => {  const content = useIntlayer("locale-switcher");  const location = useLocation();  const { availableLocales, locale, setLocale } = useLocale();  const pathWithoutLocale = () => getPathWithoutLocale(location().pathname);  return (    <div class="flex flex-row gap-2">      <For each={availableLocales}>        {(localeEl) => (          <LocalizedLink            aria-current={localeEl === locale() ? "page" : undefined}            onClick={() => setLocale(localeEl)}            params={{ locale: getPrefix(localeEl).localePrefix }}            to={pathWithoutLocale() as To}          >            {getLocaleName(localeEl)}          </LocalizedLink>        )}      </For>    </div>  );};export default LocaleSwitcher;

    in Solid files, locale from useLocale is a signal accessor. Use locale() (with parentheses) to reactively read its current value.

    To learn more about the useLocale hook, refer to the documentation.

    Step 11: Management of HTML Attributes

    As seen in Step 5, you can manage the lang and dir attributes of the html tag by using useParams in your root component. This ensures that the correct attributes are set on both the server and client.

    src/routes/__root.tsx
    const RootComponent: ParentComponent = (props) => {  const params = LocaleRoute.useParams();  const locale = params()?.locale ?? defaultLocale;  return (    <html dir={getHTMLTextDir(locale)} lang={locale}>      {/* ... */}    </html>  );};

    Step 12: Add Middleware (Optional)

    You can also use the intlayerProxy to add server-side routing to your application. This plugin will automatically detect the current locale based on the URL and set the appropriate locale cookie. If no locale is specified, the plugin will determine the most appropriate locale based on the user's browser language preferences. If no locale is detected, it will redirect to the default locale.

    Note that to use the intlayerProxy in production, you need to switch the vite-intlayer package from devDependencies to dependencies.
    vite.config.ts
    import { tanstackStart } from "@tanstack/solid-start/plugin/vite";import solid from "vite-plugin-solid";import { nitro } from "nitro/vite";import { defineConfig } from "vite";import { intlayer, intlayerProxy } from "vite-intlayer";export default defineConfig({  plugins: [    intlayerProxy(), // The Proxy should be placed before the server if you use Nitro    nitro(),    intlayer(),    tanstackStart({      router: {        routeFileIgnorePattern:          ".content.(ts|tsx|js|mjs|cjs|jsx|json|jsonc|json5)$",      },    }),    solid(),  ],});

    Step 13: Internationalise Your Metadata (Optional)

    You can also use the getIntlayer function to access your content dictionaries within the head loader for locale-aware metadata:

    src/routes/{-$locale}/index.tsx
    import { createFileRoute } from "@tanstack/solid-router";import { getIntlayer } from "intlayer";export const Route = createFileRoute("/{-$locale}/")({  component: RouteComponent,  head: ({ params }) => {    const { locale } = params;    const path = "/"; // The path for this route    const metaContent = getIntlayer("app", locale);    return {      links: [        // Canonical link: Points to the current localized page        { rel: "canonical", href: getLocalizedUrl(path, locale) },        // Hreflang: Tell Google about all localized versions        ...localeMap(({ locale: mapLocale }) => ({          rel: "alternate",          hrefLang: mapLocale,          href: getLocalizedUrl(path, mapLocale),        })),        // x-default: For users in unmatched languages        // Define the default fallback locale (usually your primary language)        {          rel: "alternate",          hrefLang: "x-default",          href: getLocalizedUrl(path, defaultLocale),        },      ],      meta: [        { title: metaContent.title },        { name: "description", content: metaContent.meta.description },      ],    };  },});

    Step 14: Retrieve the locale in your server actions (Optional)

    You may want to access the current locale from within your server actions or API endpoints. You can do this using the getLocale helper from intlayer.

    Here's an example using TanStack Start's server functions:

    src/routes/{-$locale}/index.tsx
    import { createServerFn } from "@tanstack/solid-start";import {  getRequestHeader,  getRequestHeaders,} from "@tanstack/solid-start/server";import { getCookie, getIntlayer, getLocale } from "intlayer";export const getLocaleServer = createServerFn().handler(async () => {  const locale = await getLocale({    // Get the cookie from the request (default: 'INTLAYER_LOCALE')    getCookie: (name) => {      const cookieString = getRequestHeader("cookie");      return getCookie(name, cookieString);    },    // Get the header from the request (default: 'x-intlayer-locale')    // Fallback using Accept-Language negotiation    getHeader: (name) => getRequestHeader(name),  });  // Retrieve some content using getIntlayer()  const content = getIntlayer("app", locale);  return { locale, content };});

    Step 15: Manage not found pages (Optional)

    When a user visits a non-existent page, you can display a custom not found page and the locale prefix can impact the way the not found page is triggered.

    Understanding TanStack Router's 404 handling with locale prefixes

    In TanStack Router, handling 404 pages with localised routes requires a multi-layered approach:

    1. Dedicated 404 route: A specific route to display the 404 UI
    2. Route-level validation: Validates locale prefixes and redirects invalid ones to the 404
    3. Catch-all route: Captures any non-matching paths within the locale segment
    src/routes/{-$locale}/404.tsx
    import { createFileRoute } from "@tanstack/solid-router";// This creates a dedicated /[locale]/404 route// It's used both as a direct route and imported as a component in other filesexport const Route = createFileRoute("/{-$locale}/404")({  component: NotFoundComponent,});// Exported separately so it can be reused in notFoundComponent and catch-all routesexport function NotFoundComponent() {  return (    <div>      <h1>404</h1>    </div>  );}
    src/routes/{-$locale}/route.tsx
    import { createFileRoute, Outlet, redirect } from "@tanstack/solid-router";import { validatePrefix } from "intlayer";import { NotFoundComponent } from "./404";export const Route = createFileRoute("/{-$locale}")({  // beforeLoad runs before the route renders (both server and client)  // It's the ideal place to validate the locale prefix  beforeLoad: ({ params }) => {    const localeParam = params.locale;    // validatePrefix checks if the locale is valid according to your intlayer config    const { isValid, localePrefix } = validatePrefix(localeParam);    if (!isValid) {      // Invalid locale prefix - redirect to the 404 page with a valid locale prefix      throw redirect({        to: "/{-$locale}/404",        params: { locale: localePrefix },      });    }  },  component: Outlet,  // notFoundComponent is called when a child route doesn't exist  // ex: /en/non-existent-page triggers this within the /en layout  notFoundComponent: NotFoundComponent,});
    src/routes/{-$locale}/$.tsx
    import { createFileRoute } from "@tanstack/solid-router";import { NotFoundComponent } from "./404";// The $ (splat/catch-all) route matches any path that doesn't match other routes// ex: /en/some/deeply/nested/invalid/path// This ensures ALL non-matching paths within a locale show the 404 page// Without this, deep non-matching paths could show a blank page or errorexport const Route = createFileRoute("/{-$locale}/$")({  component: NotFoundComponent,});

    (Optional) Step 16: Extract the content from your components

    If you have an existing codebase, transforming thousands of files can be time-consuming.

    To ease this process, Intlayer proposes a compiler / extractor to transform your components and extract the content.

    To set it up, you can add a compiler section in your intlayer.config.ts file:

    intlayer.config.ts
    import { type IntlayerConfig } from "intlayer";

const config: IntlayerConfig = {
  // ... Rest of your config
  compiler: {
    /**
     * Indicates whether the compiler should be enabled.
     */
    enabled: true,

    /**
     * Defines the output files path
     */
    output: ({ fileName, extension }) => `./${fileName}${extension}`,

    /**
     * Indicates whether components should be saved after being transformed.
     *
     * - If `true`, the compiler will rewrite the component file on the disk. Thus, the transformation will be permanent, and the compiler will skip the transformation for the next process. In this way, the compiler can transform the app and then it can be removed.
     *
     * - If `false`, the compiler will inject the `useIntlayer()` function call in the code only in the build output, keeping the base codebase intact. Transformation will be done only in memory.
     */
    saveComponents: false,

    /**
     * Dictionary key prefix
     */
    dictionaryKeyPrefix: "",
  },
};

export default config;

    Run the extractor to transform your components and extract the content

    bash
    npx intlayer extract

    Step 16: Generate Sitemap (Optional)

    Intlayer comes with a built-in sitemap generator to help you create a sitemap for your application easily. It handles localised routes and adds the necessary metadata for search engines.

    To use it, you first need to configure your vite.config.ts to enable pre-rendering for your localised routes and disable the default TanStack Start sitemap generation.

    vite.config.ts
    import { localeMap, localeFlatMap } from "intlayer";// ... other importsexport const pathList = ["", "/about", "/404"];const localizedPages = localeFlatMap(({ urlPrefix }) =>  pathList.map((path) => ({    path: `${urlPrefix}${path}`,    prerender: {      enabled: true,    },  })));export default defineConfig({  plugins: [    // ... other plugins    tanstackStart({      // ... other config      sitemap: {        enabled: false,      },      prerender: {        enabled: true,        crawlLinks: false,        concurrency: 10,      },      pages: localizedPages,    }),  ],});

    Then, create a src/routes/sitemap[.]xml.ts route that uses the generateSitemap function:

    src/routes/sitemap[.]xml.ts
    import { createFileRoute } from "@tanstack/solid-router";import { generateSitemap } from "intlayer";const SITE_URL = "http://localhost:3000";export const Route = createFileRoute("/sitemap.xml")({  server: {    handlers: {      GET: async () => {        const sitemap = generateSitemap(          [            { path: "/", changefreq: "daily", priority: 1.0 },            { path: "/about", changefreq: "monthly", priority: 0.8 },          ],          { siteUrl: SITE_URL }        );        return new Response(sitemap, {          headers: { "Content-Type": "application/xml" },        });      },    },  },});

    Step 17: Configure TypeScript (Optional)

    Intlayer uses module augmentation to get the benefits of TypeScript and make your codebase stronger.

    Ensure your TypeScript configuration includes the auto-generated types:

    tsconfig.json
    {  // ... your existing settings  include: [    // ... your existing includes    ".intlayer/**/*.ts", // Include the auto-generated types  ],}

    Git Configuration

    It is recommended to ignore the files generated by Intlayer. This allows you to avoid committing them to your Git repository.

    To do this, you can add the following instructions to your .gitignore file:

    .gitignore
    # Ignore the files generated by Intlayer.intlayer

    VS Code Extension

    To improve your development experience with Intlayer, you can install the official Intlayer VS Code Extension.

    Install from VS Code Marketplace

    This extension offers:

    • Autocompletion for translation keys.
    • Real-time error detection for missing translations.
    • Inline previews of translated content.
    • Quick actions to create and update translations easily.

    For more details on how to use the extension, refer to the Intlayer VS Code Extension documentation.

    Going Further

    To go further, you can implement the visual editor or externalise your content using the CMS.

    Documentation References

    Tanstack Start
    Astro