How to Get Request Headers in Express: Simple Guide

In Express, you get request headers using the req.headers object inside your route handler. This object contains all headers sent by the client as key-value pairs.

Syntax

Use req.headers inside your route handler to access all request headers as an object. Each header name is a key, and its value is the header's value.

Example parts:

• req: The request object provided by Express.
• headers: Property holding all headers.

javascript

app.get('/path', (req, res) => {
  const headers = req.headers;
  // Use headers object here
  res.send(headers);
});

Example

This example shows a simple Express server that reads and returns the request headers sent by the client.

javascript

import express from 'express';
const app = express();
const port = 3000;

app.get('/', (req, res) => {
  const headers = req.headers;
  res.json(headers);
});

app.listen(port, () => {
  console.log(`Server running at http://localhost:${port}`);
});

Output

{"host":"localhost:3000","user-agent":"curl/7.68.0","accept":"*/*"}

Common Pitfalls

Common mistakes when accessing headers in Express include:

• Trying to access headers with incorrect casing (header names are lowercase in req.headers).
• Using req.get() without knowing it returns a single header value, not all headers.
• Expecting headers to be in a different format (they are always strings).

Always use lowercase header names when accessing req.headers directly.

javascript

app.get('/wrong', (req, res) => {
  // Wrong: header names are case-sensitive keys in req.headers
  const contentType = req.headers['Content-Type']; // undefined

  // Right:
  const contentTypeCorrect = req.headers['content-type'];
  res.send(contentTypeCorrect || 'No content-type header');
});

Quick Reference

Summary tips for getting request headers in Express:

• Use req.headers to get all headers as an object.
• Header names are always lowercase keys in req.headers.
• Use req.get('Header-Name') to get a single header value case-insensitively.
• Headers values are strings; parse if needed.

Key Takeaways

Access all request headers in Express using the req.headers object.

Header names in req.headers are lowercase strings.

Use req.get('Header-Name') to retrieve a single header value case-insensitively.

Headers values are strings; convert them if you need other types.

Always check for header existence to avoid undefined errors.