Standalone Adapter

tRPC's Standalone Adapter is the simplest way to get a new project working. It's ideal for local development, and for server-based production environments. In essence it's just a wrapper around the standard Node.js HTTP Server with the normal options related to tRPC.

If you have an existing API deployment like Express, Fastify, or Next.js, which you want to integrate tRPC into, you should have a look at their respective adapters. Likewise if you have a preference to host on serverless or edge compute, we have adapters like AWS Lambda and Fetch which may fit your needs.

It's also not uncommon, where the deployed adapter is hard to run on local machines, to have 2 entry-points in your application. You could use the Standalone Adapter for local development, and a different adapter when deployed.

Example app

Description	Links
Standalone tRPC Server	StackBlitz Source
Standalone tRPC Server with CORS handling	StackBlitz Source

Setting up a Standalone tRPC Server

1. Implement your App Router

Implement your tRPC router. For example:

appRouter.ts
ts
import { initTRPC } from '@trpc/server';
import { z } from 'zod';
export const t = initTRPC.create();
export const appRouter = t.router({
  getUser: t.procedure.input(z.string()).query((opts) => {
    return { id: opts.input, name: 'Bilbo' };
  }),
  createUser: t.procedure
    .input(z.object({ name: z.string().min(5) }))
    .mutation(async (opts) => {
      // use your ORM of choice
      return await UserModel.create({
        data: opts.input,
      });
    }),
});
// export type definition of API
export type AppRouter = typeof appRouter;

appRouter.ts
ts
import { initTRPC } from '@trpc/server';
import { z } from 'zod';
export const t = initTRPC.create();
export const appRouter = t.router({
  getUser: t.procedure.input(z.string()).query((opts) => {
    return { id: opts.input, name: 'Bilbo' };
  }),
  createUser: t.procedure
    .input(z.object({ name: z.string().min(5) }))
    .mutation(async (opts) => {
      // use your ORM of choice
      return await UserModel.create({
        data: opts.input,
      });
    }),
});
// export type definition of API
export type AppRouter = typeof appRouter;

For more information you can look at the quickstart guide

2. Use the Standalone adapter

The Standalone adapter runs a simple Node.js HTTP server.

server.ts
ts
import { initTRPC } from '@trpc/server';
import { createHTTPServer } from '@trpc/server/adapters/standalone';
import { appRouter } from './appRouter.ts';
createHTTPServer({
  router: appRouter,
  createContext() {
    console.log('context 3');
    return {};
  },
}).listen(2022);

server.ts
ts
import { initTRPC } from '@trpc/server';
import { createHTTPServer } from '@trpc/server/adapters/standalone';
import { appRouter } from './appRouter.ts';
createHTTPServer({
  router: appRouter,
  createContext() {
    console.log('context 3');
    return {};
  },
}).listen(2022);

Handling CORS & OPTIONS

By default the standalone server will not respond to HTTP OPTIONS requests, or set any CORS headers.

If you're not hosting in an environment which can handle this for you, like during local development, you may need to handle it.

1. Install cors

You can add support yourself with the popular cors package

bash
yarn add cors
yarn add -D @types/cors

bash
yarn add cors
yarn add -D @types/cors

For full information on how to configure this package, check the docs

2. Configure the Standalone server

This example just throws open CORS to any request, which is useful for development, but you can and should configure it more strictly in a production environment.

server.ts
ts
import { initTRPC } from '@trpc/server';
import { createHTTPServer } from '@trpc/server/adapters/standalone';
import cors from 'cors';
createHTTPServer({
  middleware: cors(),
  router: appRouter,
  createContext() {
    console.log('context 3');
    return {};
  },
}).listen(3333);

server.ts
ts
import { initTRPC } from '@trpc/server';
import { createHTTPServer } from '@trpc/server/adapters/standalone';
import cors from 'cors';
createHTTPServer({
  middleware: cors(),
  router: appRouter,
  createContext() {
    console.log('context 3');
    return {};
  },
}).listen(3333);

The middleware option will accept any function which resembles a connect/node.js middleware, so it can be used for more than cors handling if you wish. It is, however, intended to be a simple escape hatch and as such won't on its own allow you to compose multiple middlewares together. If you want to do this then you could:

1. Use an alternate adapter with more comprehensive middleware support, like the Express adapter
2. Use a solution to compose middlewares such as connect
3. Extend the Standalone createHTTPHandler with a custom http server (see below)

Going further

createHTTPServer is returning an instance of Node's built-in http.Server(https://nodejs.org/api/http.html#class-httpserver), which means that you have an access to all it's properties and APIs. However, if createHTTPServer isn't enough for your usecase, you can also use the standalone adapter's createHTTPHandler function to create your own HTTP server. For instance:

server.ts
ts
import { createServer } from 'http';
import { initTRPC } from '@trpc/server';
import { createHTTPHandler } from '@trpc/server/adapters/standalone';
const handler = createHTTPHandler({
  router: appRouter,
  createContext() {
    return {};
  },
});
createServer((req, res) => {
  /**
   * Handle the request however you like,
   * just call the tRPC handler when you're ready
   */
  handler(req, res);
}).listen(3333);

server.ts
ts
import { createServer } from 'http';
import { initTRPC } from '@trpc/server';
import { createHTTPHandler } from '@trpc/server/adapters/standalone';
const handler = createHTTPHandler({
  router: appRouter,
  createContext() {
    return {};
  },
});
createServer((req, res) => {
  /**
   * Handle the request however you like,
   * just call the tRPC handler when you're ready
   */
  handler(req, res);
}).listen(3333);