Translate your Vite and Svelte website using Intlayer | Internationalisation (i18n)

Table of Contents

Why Intlayer over alternatives?

Compared to main solutions like svelte-i18n or i18next, Intlayer is a solution that comes with integrated optimizations such as:

Step-by-Step Guide to Set Up Intlayer in a Vite and Svelte Application

See Application Template on GitHub.

1. 1

   Install Dependencies

   Install the necessary packages using npm:

   bash

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   npx intlayer init --interactive
   

   the --interactive flag is optional. Use intlayer-cli init if you're an AI agent.

   This command will detect your environment and install the required packages. For example:

   bash

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   npm install intlayer svelte-intlayer
   npm install vite-intlayer --save-dev
   

   • intlayer

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

   • svelte-intlayer The package that integrates Intlayer with Svelte applications. It provides context providers and hooks for Svelte internationalisation.

   • vite-intlayer Includes the Vite plugin for integrating Intlayer with the Vite bundler, as well as middleware for detecting the user's preferred locale, managing cookies, and handling URL redirection.

2. 2

   Configuration of your project

   Create a config file to configure the languages of your application:

   intlayer.config.ts

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   import { Locales, type IntlayerConfig } from "intlayer";
   
   const config: IntlayerConfig = {
     internationalization: {
       locales: [
         Locales.ENGLISH,
         Locales.FRENCH,
         Locales.SPANISH,
         // Your other locales
       ],
       defaultLocale: Locales.ENGLISH,
     },
   };
   
   export default config;
   

   Through this configuration file, you can set up 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.

3. 3

   Integrate Intlayer in Your Vite Configuration

   Add the intlayer plugin into your configuration.

   vite.config.ts

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   import { defineConfig } from "vite";
   import { svelte } from "@sveltejs/vite-plugin-svelte";
   import { intlayer } from "vite-intlayer";
   
   // https://vitejs.dev/config/
   export default defineConfig({
     plugins: [svelte(), 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 Intlayer environment variables within the Vite application. Additionally, it provides aliases to optimise performance.

4. 4

   Declare Your Content

   Create and manage your content declarations to store translations:

   src/app.content.tsx

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   import { t, type Dictionary } from "intlayer";
   
   const appContent = {
     key: "app",
     content: {
       title: t({
         en: "Hello World",
         fr: "Bonjour le monde",
         es: "Hola mundo",
       }),
     },
   } satisfies Dictionary;
   
   export default appContent;
   

   Your content declarations can be defined anywhere in your application as soon as they are included in the contentDir directory (by default, ./src). And match the content declaration file extension (by default, .content.{json,ts,tsx,js,jsx,mjs,cjs,md,mdx,yaml,yml}).

   For more details, refer to the content declaration documentation.

5. 5

   Utilise Intlayer in Your Code

   src/App.svelte

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   <script>
     import { useIntlayer } from "svelte-intlayer";
   
     const content = useIntlayer("app");
   </script>
   
   <div>
   
   
   <!-- Render content as simple content  -->
   <h1>{$content.title}</h1>
   <!-- To render the content editable using the editor -->
   <h1>{@const Title = $content.title}<Title /></h1>
   <!-- To render the content as a string -->
   <div aria-label={$content.title.value}></div>
   <div aria-label={$content.title.toString()}></div>
   <div aria-label={String($content.title)}></div>
   

   If your app already exists, you can use the Intlayer Compiler, as well as the extract command, to transform thousands of components in a second.

6. 6

   Change the language of your content

   Optional

   src/App.svelte

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   <script lang="ts">
   import  { getLocaleName } from 'intlayer';
   import { useLocale } from "svelte-intlayer";
   
   // Get locale information and setLocale function
   const { locale, availableLocales, setLocale } = useLocale();
   
   // Handle locale change
   const changeLocale = (event: Event) => {
     const target = event.target as HTMLSelectElement;
     const newLocale = target.value;
     setLocale(newLocale);
   };
   </script>
   
   <div>
     <select value={$locale} on:change={changeLocale}>
       {#each availableLocales ?? [] as loc}
         <option value={loc}>
           {getLocaleName(loc)}
         </option>
       {/each}
     </select>
   </div>
   

7. 7

   Render Markdown

   Optional

   Intlayer supports rendering Markdown content directly in your Svelte application. By default, Markdown is treated as plain text. To convert Markdown into rich HTML, you can integrate @humanspeak/svelte-markdown, or another markdown parser.

   To see how to declare markdown content using the intlayer package, see the markdown doc.

   src/App.svelte

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   <script>
     import { setIntlayerMarkdown } from "svelte-intlayer";
   
     setIntlayerMarkdown((markdown) =>
      // render the markdown content as a string
      return markdown;
     );
   </script>
   
   <h1>{$content.markdownContent}</h1>
   

   You can also access your markdown front-matter data using the content.markdownContent.metadata.xxx property.

8. 8

   Set up the intlayer editor / CMS

   Optional

   To set up the intlayer editor, you must follow the intlayer editor documentation.

   To set up the intlayer CMS, you must follow the intlayer CMS documentation.

9. 7

   Add localised Routing to your application

   Optional

   To handle localised routing in your Svelte application, you can use svelte-spa-router along with Intlayer's localeFlatMap to generate routes for each locale.

   First, install svelte-spa-router:

   bash

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   npm install svelte-spa-router
   npx intlayer init
   

   Then, create a Router.svelte file to define your routes:

   src/Router.svelte

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   <script lang="ts">
   import { localeFlatMap } from "intlayer";
   import Router from "svelte-spa-router";
   import { wrap } from "svelte-spa-router/wrap";
   import App from "./App.svelte";
   
   const routes = Object.fromEntries(
       localeFlatMap(({locale, urlPrefix}) => [
       [
           urlPrefix || '/',
           wrap({
               component: App as any,
               props: {
                   locale,
               },
           }),
       ],
       ])
   );
   </script>
   
   <Router {routes} />
   

   Update your main.ts to mount the Router component instead of App:

   src/main.ts

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   import { mount } from "svelte";
   import Router from "./Router.svelte";
   
   const app = mount(Router, {
     target: document.getElementById("app")!,
   });
   
   export default app;
   

   Finally, update your App.svelte to receive the locale prop and use it with useIntlayer:

   src/App.svelte

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   <script lang="ts">
   import type { Locale } from 'intlayer';
   import { useIntlayer } from "svelte-intlayer";
   import Counter from './lib/Counter.svelte';
   import LocaleSwitcher from './lib/LocaleSwitcher.svelte';
   
   export let locale: Locale;
   
   $: content = useIntlayer('app', locale);
   </script>
   
   <main>
     <div class="locale-switcher-container">
       <LocaleSwitcher currentLocale={locale} />
     </div>
   
     <!-- ... rest of your app ... -->
   </main>
   

   Configure Server-Side Routing (Optional)

   In parallel, 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.

   Since Intlayer v9, intlayerProxy() is bundled directly into the intlayer() plugin and enabled by default through the routing.enableProxy option (true by default). Registering it separately as shown below is now optional — it is kept for backward compatibility and for setups that need to control plugin order. Set routing.enableProxy: false to opt out. See the v9 release notes.

   vite.config.ts

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   import { defineConfig } from "vite";
   import { svelte } from "@sveltejs/vite-plugin-svelte";
   import { intlayer } from "vite-intlayer";
   
   // https://vitejs.dev/config/
   export default defineConfig({
     plugins: [
       svelte(),
       intlayer({
         proxy: {
           ignore: (req) => req.url?.startsWith("/api"),
         },
       }),
     ],
   });
   

10. 8

    Change the URL when the locale changes

    Optional

    To allow users to switch languages and update the URL accordingly, you can create a LocaleSwitcher component. This component will use getLocalizedUrl from intlayer and push from svelte-spa-router.

    src/lib/LocaleSwitcher.svelte

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    <script lang="ts">
    import { getLocaleName, getLocalizedUrl } from "intlayer";
    import { useLocale } from "svelte-intlayer";
    import { push } from "svelte-spa-router";
    
    export let currentLocale: string | undefined = undefined;
    
    // Get locale information
    const { locale, availableLocales } = useLocale();
    
    // Handle locale change
    const changeLocale = (event: Event) => {
      const target = event.target as HTMLSelectElement;
      const newLocale = target.value;
      const currentUrl = window.location.pathname;
      const url = getLocalizedUrl(currentUrl, newLocale);
      push(url);
    };
    </script>
    
    <div class="locale-switcher">
      <select value={currentLocale ?? $locale} onchange={changeLocale}>
        {#each availableLocales ?? [] as loc}
          <option value={loc}>
            {getLocaleName(loc)}
          </option>
        {/each}
      </select>
    </div>
    

11. 9

    Internationalized Links

    Optional

    For SEO, it is recommended to prefix your routes with the locale (e.g., /about, /fr/about).

    src/lib/components/Link.svelte

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    <script lang="ts">
      import { getLocalizedUrl } from "intlayer";
      import { useLocale } from "svelte-intlayer";
    
      export let href = "";
      const { locale } = useLocale();
    
      // Helper to prefix URL
      $: localizedHref = getLocalizedUrl(href, $locale);
    </script>
    
    <a href={localizedHref}>
      <slot />
    </a>
    

12. 10

    Extract the content of your components

    Optional

    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

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    import { type IntlayerConfig } from "intlayer";
    
    const config: IntlayerConfig = {
      // ... Rest of your config
      compiler: {
        /**
         * Indicates if the compiler should be enabled.
         */
        enabled: true,
    
        /**
         * Defines the output files path
         */
        output: ({ fileName, extension }) => `./${fileName}${extension}`,
    
        /**
         * Indicates if the components should be saved after being transformed.
         *
         * - If `true`, the compiler will rewrite the component file in the disk. So the transformation will be permanent, and the compiler will skip the transformation for the next process. That way, the compiler can transform the app, and then it can be removed.
         *
         * - If `false`, the compiler will inject the `useIntlayer()` function call into the code in the build output only, and keep the base codebase intact. The 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

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    npx intlayer extract
    

    Since v9, the intlayerCompiler is included in the intlayer plugin. So you don't need to add it manually.

    Update your vite.config.ts to include the intlayerCompiler plugin:

    vite.config.ts

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    import { defineConfig } from "vite";
    import { intlayer, intlayerCompiler } from "vite-intlayer";
    
    export default defineConfig({
      plugins: [
        intlayer(),
        intlayerCompiler(), // Adds the compiler plugin
      ],
    });
    

    bash

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    npm run build # Or npm run dev
    

(Optional) Sitemap and robots.txt (build-time)

Intlayer includes formatters such as generateSitemap and getMultilingualUrls that produce crawler-ready multilingual sitemap.xml and robots.txt output you can write into your project’s public/ folder. In practice you run a small Node script before Vite (for example predev / prebuild npm hooks) so those files exist when you build or serve the app.

Sitemap

Intlayer’s sitemap generator respects your locale setup and includes the usual metadata for crawlers.

The generated sitemap supports the xhtml:link namespace (hreflang XML extensions). Unlike basic generators that only emit flat URLs, Intlayer wires bidirectional links between every localized variant of each page (for example /about, /fr/about, or /about?lang=fr, depending on your routing mode), which helps search engines relate localized URLs.

Robots.txt

Use getMultilingualUrls so Disallow entries cover every localized spelling of sensitive paths.

1. Add generate-seo.mjs at the project root

import fs from "fs";
import path from "path";
import { fileURLToPath } from "url";
import { generateSitemap, getMultilingualUrls } from "intlayer";

const __dirname = path.dirname(fileURLToPath(import.meta.url));

const SITE_URL = (process.env.SITE_URL || "http://localhost:5173").replace(
  /\/$/,
  ""
);

const pathList = [
  { path: "/", changefreq: "daily", priority: 1.0 },
  { path: "/about", changefreq: "monthly", priority: 0.7 },
];

const sitemapXml = generateSitemap(pathList, { siteUrl: SITE_URL });
fs.writeFileSync(path.join(__dirname, "public", "sitemap.xml"), sitemapXml);

const getAllMultilingualUrls = (urls) =>
  urls.flatMap((url) => Object.values(getMultilingualUrls(url)));

const disallowedPaths = getAllMultilingualUrls(["/admin", "/private"]);

const robotsTxt = [
  "User-agent: *",
  "Allow: /",
  ...disallowedPaths.map((path) => `Disallow: ${path}`),
  "",
  `Sitemap: ${SITE_URL}/sitemap.xml`,
].join("\n");

fs.writeFileSync(path.join(__dirname, "public", "robots.txt"), robotsTxt);

console.log("SEO files generated successfully.");

intlayer must be installed so the script can import it. Set SITE_URL in the environment for production (for example in CI).

Prefer generate-seo.mjs for Node ESM. If you use generate-seo.js instead, ensure "type": "module" is set in package.json, or run Node with ESM enabled.

2. Run the script before Vite

{
  "scripts": {
    "dev": "vite",
    "prebuild": "node generate-seo.mjs",
    "build": "vite build",
    "preview": "vite preview"
  }
}

Adjust if you use pnpm or yarn. You can also invoke the same script from CI or another step if that fits your workflow.

Git Configuration

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

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

# 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 the VS Code Marketplace

This extension provides:

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

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

Go Further

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

Frequently Asked Questions