Adapter Fetch

tRPC — Adapter: Fetch / Edge Runtimes

Setup

// Cloudflare Worker example
import { initTRPC } from '@trpc/server';
import { fetchRequestHandler } from '@trpc/server/adapters/fetch';
import type { FetchCreateContextFnOptions } from '@trpc/server/adapters/fetch';
import { z } from 'zod';

function createContext({ req, resHeaders }: FetchCreateContextFnOptions) {
  const user = req.headers.get('authorization');
  return { user, resHeaders };
}
type Context = Awaited<ReturnType<typeof createContext>>;

const t = initTRPC.context<Context>().create();

const appRouter = t.router({
  greet: t.procedure
    .input(z.object({ name: z.string() }))
    .query(({ input }) => ({ greeting: `Hello, ${input.name}!` })),
});

export type AppRouter = typeof appRouter;

export default {
  async fetch(request: Request): Promise<Response> {
    return fetchRequestHandler({
      endpoint: '/trpc',
      req: request,
      router: appRouter,
      createContext,
    });
  },
};

Core Patterns

Cloudflare Workers

import { fetchRequestHandler } from '@trpc/server/adapters/fetch';
import { createContext } from './context';
import { appRouter } from './router';

export default {
  async fetch(request: Request): Promise<Response> {
    return fetchRequestHandler({
      endpoint: '/trpc',
      req: request,
      router: appRouter,
      createContext,
    });
  },
};

Astro SSR

// src/pages/trpc/[trpc].ts
import { fetchRequestHandler } from '@trpc/server/adapters/fetch';
import type { APIRoute } from 'astro';
import { createContext } from '../../server/context';
import { appRouter } from '../../server/router';

export const ALL: APIRoute = (opts) => {
  return fetchRequestHandler({
    endpoint: '/trpc',
    req: opts.request,
    router: appRouter,
    createContext,
  });
};

Remix

// app/routes/trpc.$trpc.ts
import type { ActionFunctionArgs, LoaderFunctionArgs } from '@remix-run/node';
import { fetchRequestHandler } from '@trpc/server/adapters/fetch';
import { createContext } from '~/server/context';
import { appRouter } from '~/server/router';

function handleRequest(args: LoaderFunctionArgs | ActionFunctionArgs) {
  return fetchRequestHandler({
    endpoint: '/trpc',
    req: args.request,
    router: appRouter,
    createContext,
  });
}

export const loader = async (args: LoaderFunctionArgs) => handleRequest(args);
export const action = async (args: ActionFunctionArgs) => handleRequest(args);

Deno Deploy

import { fetchRequestHandler } from 'npm:@trpc/server/adapters/fetch';
import { createContext } from './context.ts';
import { appRouter } from './router.ts';

Deno.serve((request) => {
  return fetchRequestHandler({
    endpoint: '/trpc',
    req: request,
    router: appRouter,
    createContext,
  });
});

Limiting batch size with maxBatchSize

import { fetchRequestHandler } from '@trpc/server/adapters/fetch';
import { createContext } from './context';
import { appRouter } from './router';

export default {
  async fetch(request: Request): Promise<Response> {
    return fetchRequestHandler({
      endpoint: '/trpc',
      req: request,
      router: appRouter,
      createContext,
      maxBatchSize: 10,
    });
  },
};

Requests batching more than maxBatchSize operations are rejected with a 400 Bad Request error. Set maxItems on your client's httpBatchLink to the same value to avoid exceeding the limit.

Common Mistakes

HIGH Mismatched endpoint path in fetchRequestHandler

Wrong:

// Handler mounted at /api/trpc/[trpc] but endpoint says /trpc
fetchRequestHandler({
  endpoint: '/trpc',
  req: request,
  router: appRouter,
  createContext,
});

Correct:

// endpoint must match the actual URL path prefix
fetchRequestHandler({
  endpoint: '/api/trpc',
  req: request,
  router: appRouter,
  createContext,
});

The endpoint option tells tRPC where to strip the URL prefix to extract the procedure name. If it does not match the actual mount path, all procedures return 404 because the path parsing extracts the wrong procedure name.

Source: www/docs/server/adapters/fetch.mdx

See Also

• server-setup -- initTRPC.create(), router/procedure definition, context
• adapter-standalone -- alternative for Node.js HTTP server
• adapter-express -- alternative when Express middleware ecosystem is needed
• adapter-aws-lambda -- alternative for AWS Lambda deployments
• Cloudflare Workers docs: https://developers.cloudflare.com/workers/
• Deno Deploy docs: https://deno.com/deploy/docs