---
createdAt: 2026-03-23
updatedAt: 2026-05-06
title: Vite + Vanilla JS i18n - How to translate a Vanilla JS app in 2026
description: Discover how to make your Vite and Vanilla JS website multilingual. Follow the documentation to internationalize (i18n) and translate it.
keywords:
  - Internationalization
  - Documentation
  - Intlayer
  - Vite
  - Vanilla JS
  - JavaScript
  - TypeScript
  - HTML
slugs:
  - doc
  - environment
  - vite-and-vanilla
applicationTemplate: https://github.com/aymericzip/intlayer-vite-vanilla-template
applicationShowcase: https://intlayer-vite-vanilla.vercel.app
history:
  - version: 8.9.0
    date: 2026-05-04
    changes: "Update Solid useIntlayer API usage to direct property access"
  - version: 8.4.10
    date: 2026-03-23
    changes: "Initial history"
---

# Translate your Vite and Vanilla JS website using Intlayer | Internationalization (i18n)

<Tabs defaultTab="code">
  <Tab label="Code" value="code">

<iframe
  src="https://ide.intlayer.org/aymericzip/intlayer-vite-vanilla-template?file=intlayer.config.ts"
  className="m-auto overflow-hidden rounded-lg border-0 max-md:size-full max-md:h-[700px] md:aspect-16/9 md:w-full"
  title="Demo CodeSandbox - Intlayer"
  sandbox="allow-forms allow-modals allow-popups allow-presentation allow-same-origin allow-scripts"
  loading="lazy"
/>

  </Tab>
  <Tab label="Demo" value="demo">

<iframe
  src="https://intlayer-vite-vanilla.vercel.app"
  className="m-auto overflow-hidden rounded-lg border-0 max-md:size-full max-md:h-[700px] md:aspect-16/9 md:w-full"
  title="Demo - intlayer-vite-vanilla-template"
  sandbox="allow-forms allow-modals allow-popups allow-presentation allow-same-origin allow-scripts"
  loading="lazy"
/>

  </Tab>
</Tabs>

## Table of Contents

<TOC/>

## What is Intlayer?

**Intlayer** is an innovative, open-source internationalization (i18n) library designed to simplify multilingual support in modern web applications.

With Intlayer, you can:

- **Easily manage translations** using declarative dictionaries at the component level.
- **Dynamically localize metadata**, routes, and content.
- **Ensure TypeScript support** with autogenerated types, improving autocompletion and error detection.
- **Benefit from advanced features**, like dynamic locale detection and switching.

---

## Step-by-Step Guide to Set Up Intlayer in a Vite and Vanilla JS Application

### Step 1: Install Dependencies

Install the necessary packages using npm:

```bash packageManager="npm"
npm install intlayer vanilla-intlayer
npm install vite-intlayer --save-dev
npx intlayer init
```

```bash packageManager="pnpm"
pnpm add intlayer vanilla-intlayer
pnpm add vite-intlayer --save-dev
pnpm intlayer init
```

```bash packageManager="yarn"
yarn add intlayer vanilla-intlayer
yarn add vite-intlayer --save-dev
yarn intlayer init
```

```bash packageManager="bun"
bun add intlayer vanilla-intlayer
bun add vite-intlayer --dev
bun x intlayer init
```

- **intlayer**
  The core package that provides internationalization tools for configuration management, translation, [content declaration](https://github.com/aymericzip/intlayer/blob/main/docs/docs/en/dictionary/content_file.md), transpilation, and [CLI commands](https://github.com/aymericzip/intlayer/blob/main/docs/docs/en/cli/index.md).

- **vanilla-intlayer**
  The package that integrates Intlayer with plain JavaScript / TypeScript applications. It provides a pub/sub singleton (`IntlayerClient`) and callback-based helpers (`useIntlayer`, `useLocale`, etc.) so any part of your app can react to locale changes without depending on a UI framework.

- **vite-intlayer**
  Includes the Vite plugin for integrating Intlayer with the [Vite bundler](https://vite.dev/guide/why.html#why-bundle-for-production), as well as middleware for detecting the user's preferred locale, managing cookies, and handling URL redirection.

### Step 2: Configuration of your project

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

```typescript fileName="intlayer.config.ts" codeFormat={["typescript", "esm", "commonjs"]}
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 localized 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](https://github.com/aymericzip/intlayer/blob/main/docs/docs/en/configuration.md).

### Step 3: Integrate Intlayer in Your Vite Configuration

Add the intlayer plugin into your configuration.

```typescript fileName="vite.config.ts" codeFormat={["typescript", "esm", "commonjs"]}
import { defineConfig } from "vite";
import { intlayer } from "vite-intlayer";

// https://vitejs.dev/config/
export default defineConfig({
  plugins: [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 optimize performance.

### Step 4: Bootstrap Intlayer in your entry point

Call `installIntlayer()` **before** any content is rendered so that the global locale singleton is ready.

```typescript fileName="src/main.ts" codeFormat="typescript"
import { installIntlayer } from "vanilla-intlayer";

// Must be called before rendering any i18n content.
installIntlayer();

// Import and run your app modules.
import "./app.js";
```

If you also use `md()` content declarations (Markdown), install the markdown renderer as well:

```typescript fileName="src/main.ts" codeFormat="typescript"
import { installIntlayer, installIntlayerMarkdown } from "vanilla-intlayer";

installIntlayer();
installIntlayerMarkdown();

import "./app.js";
```

### Step 5: Declare Your Content

Create and manage your content declarations to store translations:

```typescript fileName="src/app.content.ts" contentDeclarationFormat={["typescript", "esm", "commonjs"]}
import { insert, t, type Dictionary } from "intlayer";

const appContent = {
  key: "app",
  content: {
    title: "Vite + Vanilla",

    viteLogoLabel: t({
      en: "Vite Logo",
      fr: "Logo Vite",
      es: "Logo Vite",
    }),

    count: insert(
      t({
        en: "count is {{count}}",
        fr: "le compte est {{count}}",
        es: "el recuento es {{count}}",
      })
    ),

    readTheDocs: t({
      en: "Click on the Vite logo to learn more",
      fr: "Cliquez sur le logo Vite pour en savoir plus",
      es: "Haga clic en el logotipo de Vite para obtener más información",
    }),
  },
} satisfies Dictionary;

export default appContent;
```

```json fileName="src/app.content.json" contentDeclarationFormat="json"
{
  "$schema": "https://intlayer.org/schema.json",
  "key": "app",
  "content": {
    "title": "Vite + Vanilla",
    "viteLogoLabel": {
      "nodeType": "translation",
      "translation": {
        "en": "Vite Logo",
        "fr": "Logo Vite",
        "es": "Logo Vite"
      }
    },
    "count": {
      "nodeType": "insertion",
      "insertion": {
        "nodeType": "translation",
        "translation": {
          "en": "count is {{count}}",
          "fr": "le compte est {{count}}",
          "es": "el recuento es {{count}}"
        }
      }
    },
    "readTheDocs": {
      "nodeType": "translation",
      "translation": {
        "en": "Click on the Vite logo to learn more",
        "fr": "Cliquez sur le logo Vite pour en savoir plus",
        "es": "Haga clic en el logotipo de Vite para obtener más información"
      }
    }
  }
}
```

> 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}`).
>
> For more details, refer to the [content declaration documentation](https://github.com/aymericzip/intlayer/blob/main/docs/docs/en/dictionary/content_file.md).

### Step 6: Use Intlayer in Your JavaScript

`vanilla-intlayer` mirrors the `react-intlayer` surface API: `useIntlayer(key, locale?)` returns the translated content directly. Chain `.onChange()` on the result to subscribe to locale changes - the explicit equivalent of a React re-render.

```typescript fileName="src/main.ts" codeFormat="typescript"
import { installIntlayer, useIntlayer } from "vanilla-intlayer";

installIntlayer();

// Get the initial content for the current locale.
// Chain .onChange() to be notified whenever the locale changes.
const content = useIntlayer("app").onChange((newContent) => {
  // Re-render or patch only the affected DOM nodes
  document.querySelector<HTMLHeadingElement>("h1")!.textContent = String(
    newContent.title
  );
  document.querySelector<HTMLParagraphElement>(".read-the-docs")!.textContent =
    String(newContent.readTheDocs);
});

// Initial render
document.querySelector<HTMLHeadingElement>("h1")!.textContent = String(
  content.title
);
document.querySelector<HTMLParagraphElement>(".read-the-docs")!.textContent =
  String(content.readTheDocs);
```

> Access leaf values as strings by wrapping them in `String()`, which calls the node's `toString()` method and returns the translated text.
>
> When you need the value for a native HTML attribute (e.g. `alt`, `aria-label`), use `.value` directly:
>
> ```typescript
> img.alt = content.viteLogoLabel.value;
> ```

### (Optional) Step 7: Change the language of your content

To change the language of your content, use the `setLocale` function exposed by `useLocale`.

```typescript fileName="src/locale-switcher.ts" codeFormat="typescript"
import { getLocaleName } from "intlayer";
import { useLocale } from "vanilla-intlayer";

export function setupLocaleSwitcher(container: HTMLElement): () => void {
  const { locale, availableLocales, setLocale, subscribe } = useLocale();

  const select = document.createElement("select");
  select.setAttribute("aria-label", "Language");

  const render = (currentLocale: string) => {
    select.innerHTML = availableLocales
      .map(
        (loc) =>
          `<option value="${loc}"${loc === currentLocale ? " selected" : ""}>
            ${getLocaleName(loc)}
          </option>`
      )
      .join("");
  };

  render(locale);
  container.appendChild(select);

  select.addEventListener("change", () => setLocale(select.value as any));

  // Keep the dropdown in sync when locale changes from elsewhere
  return subscribe((newLocale) => render(newLocale));
}
```

### (Optional) Step 8: Render Markdown and HTML content

Intlayer supports `md()` and `html()` content declarations. In vanilla JS, compiled output is inserted as raw HTML via `innerHTML`.

```typescript fileName="src/app.content.ts" contentDeclarationFormat=["typescript", "esm", "cjs"]
import { md, t, type Dictionary } from "intlayer";

const appContent = {
  key: "app",
  content: {
    // ...
    editNote: md(
      t({
        en: "Edit `src/main.ts` and save to test **HMR**",
        fr: "Modifiez `src/main.ts` et enregistrez pour tester **HMR**",
        es: "Edite `src/main.ts` y guarde para probar **HMR**",
      })
    ),
  },
} satisfies Dictionary;

export default appContent;
```

Compile and inject the HTML:

```typescript fileName="src/main.ts" codeFormat="typescript"
import {
  compileMarkdown,
  installIntlayerMarkdown,
  useIntlayer,
} from "vanilla-intlayer";

installIntlayerMarkdown();

const content = useIntlayer("app").onChange((newContent) => {
  const el = document.querySelector<HTMLDivElement>(".edit-note")!;
  el.innerHTML = compileMarkdown(String(newContent.editNote));
});

document.querySelector<HTMLDivElement>(".edit-note")!.innerHTML =
  compileMarkdown(String(content.editNote));
```

> [!TIP]
> `String(content.editNote)` calls `toString()` on the `IntlayerNode` which returns the raw Markdown string. Pass it to `compileMarkdown` to get an HTML string, then set it via `innerHTML`.

> [!WARNING]
> Only use `innerHTML` with trusted content. If the markdown comes from user input, sanitize it first (e.g. with DOMPurify). You can install a sanitizing renderer dynamically:
>
> ```typescript
> import { installIntlayerMarkdownDynamic } from "vanilla-intlayer";
>
> await installIntlayerMarkdownDynamic(async () => {
>   const DOMPurify = await import("dompurify");
>   return (markdown) => DOMPurify.sanitize(compileMarkdown(markdown));
> });
> ```

### (Optional) Step 9: Add localized Routing to your application

To make unique routes for each language (useful for SEO), you can use `intlayerProxy` in your Vite config for server-side locale detection.

First, add `intlayerProxy` to your Vite config:

> Note that to use `intlayerProxy` in production, you need to move `vite-intlayer` from `devDependencies` to `dependencies`.

```typescript {3,7} fileName="vite.config.ts" codeFormat={["typescript", "esm", "commonjs"]}
import { defineConfig } from "vite";
import { intlayer, intlayerProxy } from "vite-intlayer";

export default defineConfig({
  plugins: [
    intlayerProxy(), // should be placed first
    intlayer(),
  ],
});
```

### (Optional) Step 10: Change the URL when the locale changes

To update the browser URL when the locale changes, call `useRewriteURL()` after installing Intlayer:

```typescript fileName="src/main.ts" codeFormat="typescript"
import { installIntlayer, useRewriteURL } from "vanilla-intlayer";

installIntlayer();

// Rewrites the URL immediately and on every subsequent locale change.
// Returns an unsubscribe function for cleanup.
const stopRewriteURL = useRewriteURL();
```

### (Optional) Step 11: Switch the HTML Language and Direction Attributes

Update the `<html>` tag's `lang` and `dir` attributes to match the current locale for accessibility and SEO.

```typescript fileName="src/main.ts" codeFormat="typescript"
import { getHTMLTextDir } from "intlayer";
import { installIntlayer, useLocale } from "vanilla-intlayer";

installIntlayer();

useLocale({
  onLocaleChange: (locale) => {
    document.documentElement.lang = locale;
    document.documentElement.dir = getHTMLTextDir(locale);
  },
});
```

### (Optional) Step 12: Lazy-load dictionaries per locale

For large apps you may want to split each locale's dictionary into its own chunk. Use `useDictionaryDynamic` alongside Vite's dynamic `import()`:

```typescript fileName="src/app.ts" codeFormat="typescript"
import { installIntlayer, useDictionaryDynamic } from "vanilla-intlayer";

installIntlayer();

const unsubscribe = useDictionaryDynamic(
  {
    en: () => import("../.intlayer/dictionaries/en/app.mjs"),
    fr: () => import("../.intlayer/dictionaries/fr/app.mjs"),
    es: () => import("../.intlayer/dictionaries/es/app.mjs"),
  },
  "app"
).onChange((content) => {
  document.querySelector("h1")!.textContent = String(content.title);
});
```

> Each locale's bundle is fetched only when that locale becomes active and the result is cached - subsequent switches to the same locale are instant.

### (Optional) Step 13: Extract the content of your components

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

To ease this process, Intlayer proposes a [compiler](https://github.com/aymericzip/intlayer/blob/main/docs/docs/en/compiler.md) / [extractor](https://github.com/aymericzip/intlayer/blob/main/docs/docs/en/cli/extract.md) to transform your components and extract the content.

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

```typescript fileName="intlayer.config.ts" codeFormat="typescript"
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;
```

<Tabs>
 <Tab value='Extract command'>

Run the extractor to transform your components and extract the content

```bash packageManager="npm"
npx intlayer extract
```

```bash packageManager="pnpm"
pnpm intlayer extract
```

```bash packageManager="yarn"
yarn intlayer extract
```

```bash packageManager="bun"
bun x intlayer extract
```

 </Tab>
 <Tab value='Babel compiler'>

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

```ts fileName="vite.config.ts"
import { defineConfig } from "vite";
import { intlayer, intlayerCompiler } from "vite-intlayer";

export default defineConfig({
  plugins: [
    intlayer(),
    intlayerCompiler(), // Adds the compiler plugin
  ],
});
```

```bash packageManager="npm"
npm run build # Or npm run dev
```

```bash packageManager="pnpm"
pnpm run build # Or pnpm run dev
```

```bash packageManager="yarn"
yarn build # Or yarn dev
```

```bash packageManager="bun"
bun run build # Or bun run dev
```

 </Tab>
</Tabs>

### (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

```javascript fileName="generate-seo.mjs"
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

```json fileName="package.json"
{
  "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.

### Configure TypeScript

Ensure your TypeScript configuration includes the autogenerated types.

```json5 fileName="tsconfig.json"
{
  "compilerOptions": {
    // ...
  },
  "include": ["src", ".intlayer/**/*.ts"],
}
```

### 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:

```bash
# 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](https://marketplace.visualstudio.com/items?itemName=intlayer.intlayer-vs-code-extension)

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](https://intlayer.org/doc/vs-code-extension).

---

### Go Further

To go further, you can implement the [visual editor](https://github.com/aymericzip/intlayer/blob/main/docs/docs/en/intlayer_visual_editor.md) or externalize your content using the [CMS](https://github.com/aymericzip/intlayer/blob/main/docs/docs/en/intlayer_CMS.md).
