express.urlencoded() Function

express.urlencoded() parses form data sent with Content-Type: application/x-www-form-urlencoded and makes it available as an object on req.body.

Syntax

app.use(
    express.urlencoded({
        extended: true,
        inflate: true,
        limit: "1mb",
        parameterLimit: 5000,
    })
);

• extended: true — allows nested objects/arrays via the qs library.
• inflate — auto-decompresses gzip/deflate bodies.
• limit — caps request body size.
• parameterLimit — caps the number of form fields.

Example: a simple sign-up form

const express = require("express");
const app = express();
const PORT = 4500;

app.use(express.urlencoded({ extended: true }));

app.get("/signup", (req, res) => {
    res.send(
        "<form method=POST action=/signup><input name=email><input name=age type=number><button>Join</button></form>"
    );
});

app.post("/signup", (req, res) => {
    console.log(req.body);
    res.send("Signup data received");
});

app.listen(PORT, () => console.log(`Listening on ${PORT}`));

Submitting the form logs the parsed email and age fields on the server.

Where it's commonly used

• Login and sign-up forms.
• Contact or feedback forms.
• Checkout/order forms in e-commerce apps.
• Survey responses submitted via HTML forms.
• Profile-update forms in dashboards.