Helmet

Helmet helps you secure your Express apps by setting various HTTP headers. It's not a silver bullet, but it can help!

Looking for a version of Helmet that supports the Koa framework?

Quick start

First, run npm install helmet --save for your app. Then, in an Express (or Connect) app:

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

const app = express();

app.use(helmet());

// ...

It's best to use Helmet early in your middleware stack so that its headers are sure to be set.

You can also use its pieces individually:

app.use(helmet.xssFilter());
app.use(helmet.frameguard());

You can disable a middleware that's normally enabled by default. This will disable frameguard but include the other defaults.

app.use(
  helmet({
    frameguard: false,
  })
);

You can also set options for a middleware. Setting options like this will always include the middleware, whether or not it's a default.

app.use(
  helmet({
    frameguard: {
      action: "deny",
    },
  })
);

If you're using Express 3, make sure these middlewares are listed before app.router.

How it works

Helmet is a collection of 11 smaller middleware functions that set HTTP response headers. Running app.use(helmet()) will not include all of these middleware functions by default.

Module	Default?
contentSecurityPolicy for setting Content Security Policy
crossdomain for handling Adobe products' crossdomain requests
dnsPrefetchControl controls browser DNS prefetching	✓
expectCt for handling Certificate Transparency
frameguard to prevent clickjacking	✓
hidePoweredBy to remove the X-Powered-By header	✓
hsts for HTTP Strict Transport Security	✓
ieNoOpen sets X-Download-Options for IE8+	✓
noSniff to keep clients from sniffing the MIME type	✓
referrerPolicy to hide the Referer header
xssFilter adds some small XSS protections	✓

You can see more in the documentation.