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tRPC

Server-Side Rendering

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To enable SSR just set ssr: true in your createTRPCNext config callback.

In order to execute queries properly during the server-side render step we need to add extra logic inside our config:

Additionally, consider Response Caching.

utils/trpc.ts
import { httpBatchLink } from '@trpc/client';
import { createTRPCNext } from '@trpc/next';
import superjson from 'superjson';
import type { AppRouter } from './api/trpc/[trpc]';

export const trpc = createTRPCNext<AppRouter>({
  config(config) {
    const { ctx } = opts;
    if (typeof window !== 'undefined') {
      // during client requests
      return {
        transformer: superjson, // optional - adds superjson serialization
        links: [
          httpBatchLink({
            url: '/api/trpc',
          }),
        ],
      };
    }

    return {
      transformer: superjson, // optional - adds superjson serialization
      links: [
        httpBatchLink({
          // The server needs to know your app's full url
          url: `${getBaseUrl()}/api/trpc`,
          /**
           * Set custom request headers on every request from tRPC
           * @see https://trpc.io/docs/v10/header
           */
          headers() {
            if (!ctx?.req?.headers) {
              return {};
            }
            // To use SSR properly, you need to forward client headers to the server
            // This is so you can pass through things like cookies when we're server-side rendering
            return {
              cookie: ctx.req.headers.cookie,
            };
          },
        }),
      ],
    };
  },
  ssr: true,
});

or, if you want to SSR conditional on a given request, you can pass a callback to ssr. This callback can return a boolean, or a Promise resolving to a boolean:

utils/trpc.ts
import { httpBatchLink } from '@trpc/client';
import { createTRPCNext } from '@trpc/next';
import superjson from 'superjson';
import type { AppRouter } from './api/trpc/[trpc]';

export const trpc = createTRPCNext<AppRouter>({
  config(config) {
    const { ctx } = opts;
    if (typeof window !== 'undefined') {
      // during client requests
      return {
        transformer: superjson, // optional - adds superjson serialization
        links: [
          httpBatchLink({
            url: '/api/trpc',
          }),
        ],
      };
    }

    return {
      transformer: superjson, // optional - adds superjson serialization
      links: [
        httpBatchLink({
          // The server needs to know your app's full url
          url: `${getBaseUrl()}/api/trpc`,
          /**
           * Set custom request headers on every request from tRPC
           * @see https://trpc.io/docs/v10/header
           */
          headers() {
            if (!ctx?.req?.headers) {
              return {};
            }
            // To use SSR properly, you need to forward client headers to the server
            // This is so you can pass through things like cookies when we're server-side rendering
            return {
              cookie: ctx.req.headers.cookie,
            };
          },
        }),
      ],
    };
  },
  ssr(opts) {
    // only SSR if the request is coming from a bot
    return opts.ctx?.req?.headers['user-agent']?.includes('bot');
  },
});
pages/_app.tsx
import { trpc } from '~/utils/trpc';
import type { AppProps } from 'next/app';
import React from 'react';

const MyApp: AppType = ({ Component, pageProps }: AppProps) => {
  return <Component {...pageProps} />;
};

export default trpc.withTRPC(MyApp);

FAQ

Q: Why do I need to forward the client's headers to the server manually? Why doesn't tRPC automatically do that for me?

While it's rare that you wouldn't want to forward the client's headers to the server when doing SSR, you might want to add things dynamically in the headers. Therefore, tRPC doesn't want to take responsibility for header keys colliding, etc.

Q: Why do I need to delete the connection header when using SSR on Node 18?

If you don't remove the connection header, the data fetching will fail with TRPCClientError: fetch failed because connection is a forbidden header name.

Q: Why do I still see network requests being made in the Network tab?

By default, @tanstack/react-query (which we use for the data fetching hooks) refetches data on mount and window refocus, even if it's already got initial data via SSR. This ensures data is always up-to-date. See the page on SSG if you'd like to disable this behavior.