express.raw() Function

express.raw() is built-in middleware that reads an incoming request body into a Buffer rather than parsing it as JSON or text. It's the go-to choice when the payload is raw binary data.

Syntax

express.raw([options])

options supports properties like inflate, limit, and type.

With the middleware

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

app.use(express.raw());

app.post("/upload-cover", (req, res) => {
    console.log(req.body); // a Buffer
    res.send(`Received ${req.body.length} bytes`);
});

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

Sending a POST request with Content-Type: application/octet-stream and a binary body results in req.body being a Buffer containing the raw bytes.

Without the middleware

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

app.post("/upload-cover", (req, res) => {
    console.log(req.body); // undefined
    res.end();
});

Without express.raw(), Express has no idea how to interpret the body, so req.body stays undefined.

Use cases

Accepting file uploads sent as raw bytes.
Handling webhook payloads that require verifying the raw body (e.g. signature checks).
Working with binary protocols instead of JSON or form data.