SvelteKit change lang attribute

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Demo & Repo

I wondered, if I’m asked to build a showcase website with internationalisation, what tech should I choose? Since I really like component base flow, like in Svelte and Vue, especially scoped styling, I was curious to see if it will be a hassle to do with SvelteKit, a project I’m quite interested in.

SvelteKit doesn’t have, at least in time of writing, the option to change the lang attribute of <html> depending on route path. But it’s easily doable with hooks.

For this example, @sveltejs/adapter-static is used to prerender the entire website, a kind of SSG.

Let’s begin by creating a SvelteKit project and installing the above-mentioned adapter (don’t forget to follow instructions on how to use it).

npm init svelte@next demo
cd demo
npm i
npm i -D @sveltejs/adapter-static@next

We have our english version at /, then french at /fr, and ukrainian at /ua

Routes folder looks like this.

 └─ ua
     └─ index.svelte
 └─ fr
     └─ index.svelte
 └─ index.svelte

Now markup.

<!-- ~/routes/+layouts.svelte -->

	<nav class="ce">
		<a href="/">🇬🇧</a>
		<a href="/fr">🇫🇷</a>
		<a href="/ua">🇺🇦</a>

		<slot />

The +layout.js file in route directory should include.

export const csr = false;
export const prerender = true;

A little bit of HTML for each route.

<!-- ~/routes/index.svelte -->

<h1>Hello World</h1>
<!-- ~/routes/fr/index.svelte -->

<h1>Bonjour le Monde</h1>
<!-- ~/routes/ua/index.svelte -->

<h1>Привіт Світе</h1>

And finally hooks.js.

/* ~/src/hooks.js */

/** @type {import('@sveltejs/kit').Handle} */
export async function handle({ request, resolve }) {
	const response = await resolve(request);

	if (request.path.startsWith('/fr')) {
		return {
			// @ts-ignore
			body: response.body?.replace('<html lang="en">', '<html lang="fr">'),

	if (request.path.startsWith('/ua')) {
		return {
			// @ts-ignore
			body: response.body?.replace('<html lang="en">', '<html lang="uk">'),

	return response;

To build and then preview on localhost:5173.

npm run build
npm run preview

The site is not in SPA mode, so on every navigation page will reload.

How to do it in SPA mode and change lang on the fly? I suppose we can just watch the path property in the page object inside +layout.svelte and then update <html> accordingly.