Send cookies cross-origin

If your API resides on a different origin than your front-end and you wish to send cookies to it, you will need to enable CORS on your server and send cookies with your requests by providing the option {credentials: "include"} to fetch.

The arguments provided to the fetch function used by tRPC can be modified as follows.

app.ts
ts
import { createTRPCClient, httpBatchLink } from '@trpc/client';
import type { AppRouter } from './server';
 
const client = createTRPCClient<AppRouter>({
  links: [
    httpBatchLink({
      url: 'YOUR_SERVER_URL',
      fetch(url, options) {
        return fetch(url, {
          ...options,
          credentials: 'include',
        });
      },
    }),
  ],
});

app.ts
ts
import { createTRPCClient, httpBatchLink } from '@trpc/client';
import type { AppRouter } from './server';
 
const client = createTRPCClient<AppRouter>({
  links: [
    httpBatchLink({
      url: 'YOUR_SERVER_URL',
      fetch(url, options) {
        return fetch(url, {
          ...options,
          credentials: 'include',
        });
      },
    }),
  ],
});

info

You also need to enable CORS on your server by modifying your adapter, or the HTTP server which fronts your API. The best way to do this varies adapter-by-adapter and based on your hosting infrastructure, and individual adapters generally document this process where applicable.