How to enable CORS — Basic — app-wide

Node / Express Application-level middleware

Apply the cors middleware on the Express app so all routes allow cross-origin requests.

Learn: Browsers block cross-origin API calls unless the server sends CORS headers. App-wide CORS is simplest when a single frontend origin talks to your API. Tighten options in production—avoid `origin: '*'` if cookies or credentials matter.

Supplementary examples

Default CORS for all routes

const cors = require("cors");
app.use(cors());

Restrict to one frontend origin

app.use(
  cors({
    origin: process.env.FRONTEND_URL || "http://localhost:3000",
    credentials: true,
  })
);

Course example

const logger = require("./config/logger");
const app = express();
app.use(logger);
app.use(cors());
app.use(express.json());
// Some code omitted for brevity

Additional references & examples

cors package (npm)
Configuration options for CORS middleware.
Express.js guide
Routing, middleware order, and request/response lifecycle.