paraglideMiddleware()

paraglideMiddleware<T>(request, resolve, callbacks?): Promise<Response>

Defined in: server/middleware.js:64

Server middleware that handles locale-based routing and request processing.

This middleware performs several key functions:

1. Determines the locale for the incoming request using configured strategies
2. Handles URL localization and redirects (only for document requests)
3. Maintains locale state using AsyncLocalStorage to prevent request interference

When URL strategy is used:

• The locale is extracted from the URL for all request types
• If URL doesn't match the determined locale, redirects to localized URL (only for document requests)
• De-localizes URLs before passing to server (e.g., /fr/about → /about)

Type Parameters

T

T

The return type of the resolve function

Parameters

request

Request

The incoming request object

resolve

(args) => T | Promise<T>

Function to handle the request

callbacks?

Callbacks to handle events from middleware

onRedirect

(response) => void

Returns

Promise<Response>

Examples

// Basic usage in metaframeworks like NextJS, SvelteKit, Astro, Nuxt, etc.
export const handle = async ({ event, resolve }) => {
  return serverMiddleware(event.request, ({ request, locale }) => {
    // let the framework further resolve the request
    return resolve(request);
  });
};

// Usage in a framework like Express JS or Hono
app.use(async (req, res, next) => {
  const result = await serverMiddleware(req, ({ request, locale }) => {
    // If a redirect happens this won't be called
    return next(request);
  });
});

// Usage in serverless environments like Cloudflare Workers
// ⚠️ WARNING: This should ONLY be used in serverless environments like Cloudflare Workers.
// Disabling AsyncLocalStorage in traditional server environments risks cross-request pollution where state from
// one request could leak into another concurrent request.
export default {
  fetch: async (request) => {
    return serverMiddleware(
      request,
      ({ request, locale }) => handleRequest(request, locale),
      { disableAsyncLocalStorage: true }
    );
  }
};