Express Adapter

Example app

Description	Links
Express server & procedure calls with Node.js.	CodeSandbox Source

How to add tRPC to existing Express project

1. Install deps

bash
yarn add @trpc/server zod

bash
yarn add @trpc/server zod

Zod isn't a required dependency, but it's used in the sample router below.

AI Agents

If you use an AI coding agent, install tRPC skills for better code generation:

bash
npx @tanstack/intent@latest install

bash
npx @tanstack/intent@latest install

2. Create a tRPC router

Implement your tRPC router. A sample router is given below:

server.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) => {
    opts.input; // string
    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 { id: '1', ...opts.input };
    }),
});
 
// export type definition of API
export type AppRouter = typeof appRouter;

server.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) => {
    opts.input; // string
    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 { id: '1', ...opts.input };
    }),
});
 
// export type definition of API
export type AppRouter = typeof appRouter;

If your router file starts getting too big, split your router into several subrouters each implemented in its own file. Then merge them into a single root appRouter.

3. Use the Express adapter

tRPC includes an adapter for Express out of the box. This adapter lets you convert your tRPC router into an Express middleware.

server.ts
ts
import { initTRPC } from '@trpc/server';
import * as trpcExpress from '@trpc/server/adapters/express';
import express from 'express';
 
// created for each request
const createContext = ({
  req,
  res,
}: trpcExpress.CreateExpressContextOptions) => ({}); // no context
type Context = Awaited<ReturnType<typeof createContext>>;
 
const t = initTRPC.context<Context>().create();
const appRouter = t.router({
  // [...]
});
 
const app = express();
 
app.use(
  '/trpc',
  trpcExpress.createExpressMiddleware({
    router: appRouter,
    createContext,
  }),
);
 
app.listen(4000);

server.ts
ts
import { initTRPC } from '@trpc/server';
import * as trpcExpress from '@trpc/server/adapters/express';
import express from 'express';
 
// created for each request
const createContext = ({
  req,
  res,
}: trpcExpress.CreateExpressContextOptions) => ({}); // no context
type Context = Awaited<ReturnType<typeof createContext>>;
 
const t = initTRPC.context<Context>().create();
const appRouter = t.router({
  // [...]
});
 
const app = express();
 
app.use(
  '/trpc',
  trpcExpress.createExpressMiddleware({
    router: appRouter,
    createContext,
  }),
);
 
app.listen(4000);

Your endpoints are now available via HTTP!

Endpoint	HTTP URI
getUser	GET http://localhost:4000/trpc/getUser?input=INPUT where INPUT is a URI-encoded JSON string.
createUser	POST http://localhost:4000/trpc/createUser with req.body of type {name: string}