# Source: https://www.better-auth.com/llms.txt/docs/integrations/express.md

# Express Integration

Integrate Better Auth with Express.



This guide will show you how to integrate Better Auth with [express.js](https://expressjs.com/).

Before you start, make sure you have a Better Auth instance configured. If you haven't done that yet, check out the [installation](/docs/installation).

<Callout>
  Note that CommonJS (cjs) isn't supported. Use ECMAScript Modules (ESM) by setting `"type": "module"` in your `package.json` or configuring your `tsconfig.json` to use ES modules.
</Callout>

### Mount the handler

To enable Better Auth to handle requests, we need to mount the handler to an API route. Create a catch-all route to manage all requests to `/api/auth/*` in case of ExpressJS v4 or `/api/auth/*splat` in case of ExpressJS v5 (or any other path specified in your Better Auth options).

<Callout type="warn">
  Donât use `express.json()` before the Better Auth handler. Use it only for other routes, or the client API will get stuck on "pending".
</Callout>

```ts title="server.ts"
import express from "express";
import { toNodeHandler } from "better-auth/node";
import { auth } from "./auth";

const app = express();
const port = 3005;

app.all("/api/auth/*", toNodeHandler(auth)); // For ExpressJS v4
// app.all("/api/auth/*splat", toNodeHandler(auth)); For ExpressJS v5 

// Mount express json middleware after Better Auth handler
// or only apply it to routes that don't interact with Better Auth
app.use(express.json());

app.listen(port, () => {
	console.log(`Example app listening on port ${port}`);
});
```

After completing the setup, start your server. Better Auth will be ready to use. You can send a `GET` request to the `/ok` endpoint (`/api/auth/ok`) to verify that the server is running.

### Cors Configuration

To add CORS (Cross-Origin Resource Sharing) support to your Express server when integrating Better Auth, you can use the `cors` middleware. Below is an updated example showing how to configure CORS for your server:

```ts
import express from "express";
import cors from "cors"; // Import the CORS middleware
import { toNodeHandler, fromNodeHeaders } from "better-auth/node";
import { auth } from "./auth";

const app = express();
const port = 3005;

// Configure CORS middleware
app.use(
  cors({
    origin: "http://your-frontend-domain.com", // Replace with your frontend's origin
    methods: ["GET", "POST", "PUT", "DELETE"], // Specify allowed HTTP methods
    credentials: true, // Allow credentials (cookies, authorization headers, etc.)
  })
);
```

### Getting the User Session

To retrieve the user's session, you can use the `getSession` method provided by the `auth` object. This method requires the request headers to be passed in a specific format. To simplify this process, Better Auth provides a `fromNodeHeaders` helper function that converts Node.js request headers to the format expected by Better Auth (a `Headers` object).

Here's an example of how to use `getSession` in an Express route:

```ts title="server.ts"
import { fromNodeHeaders } from "better-auth/node";
import { auth } from "./auth"; // Your Better Auth instance

app.get("/api/me", async (req, res) => {
 	const session = await auth.api.getSession({
      headers: fromNodeHeaders(req.headers),
    });
	return res.json(session);
});
```