Custom Request and Response objects in Express with TypeScript

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If you use TypeScript and Express you might want to put some custom properties on the Request and Response objects or have a custom User object. This is how you do it.

Add type definitions

Add a folder called "type-definitions" to your project. In that folder create a file called "express.d.ts". This is where you will put your custom types.

import { CustomUser } from "../src/models/user.js";

declare global {
  namespace Express {
    // extend the built in User with your own custom properties
    interface User extends CustomUser {}

    // Extend the request and response objects with your own custom properties
    export interface Request {
      parsedForm?: SomeCustomType;
    export interface Response {
      locals: {
        allowedRoles?: string[];

Tell typescript about your custom types

Now add the following to your tsconfig.json file:

  "compilerOptions": {
    "types": ["./type-defs/express-request-merging.d.ts"]

Now you can use your custom types in your code

middleware(req:Express.Request, res:Express.Response) {
  // req.parsedForm is now available
  // res.locals.allowedRoles is now available
  // req.user is now available with custom props