HTTP Strict Transport Security middleware

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This middleware adds the Strict-Transport-Security header to the response. This tells browsers, "hey, only use HTTPS for the next period of time". (See the spec for more.)

This will set the Strict Transport Security header, telling browsers to visit by HTTPS for the next 180 days:

var hsts = require('hsts')
 
app.use(hsts({
  maxAge: 15552000  // 180 days in seconds 
}))
// Strict-Transport-Security: max-age: 15552000; includeSubDomains 

Note that the max age must be in seconds. This was different in previous versions of this module!

The includeSubDomains directive is present by default. If this header is set on example.com, supported browsers will also use HTTPS on my-subdomain.example.com. You can disable this:

app.use(hsts({
  maxAge: 15552000,
  includeSubDomains: false
}))

Chrome lets you submit your site for baked-into-Chrome HSTS by adding preload to the header. You can add that with the following code, and then submit your site to the Chrome team at hstspreload.appspot.com.

app.use(hsts({
  maxAge: 10886400,        // Must be at least 18 weeks to be approved by Google 
  includeSubDomains: true, // Must be enabled to be approved by Google 
  preload: true
}))

This header will be set req.secure is true, a boolean auto-populated by Express. If you're not using Express, that value won't necessarily be set, so you have two options:

// Set the header based on a condition 
app.use(hsts({
  maxAge: 1234000,
  setIf: function (req, res) {
    return req.secure || (req.headers['x-forwarded-proto'] === 'https')
  }
}))
 
// ALWAYS set the header 
app.use(hsts({
  maxAge: 1234000,
  force: true
}))

This only works if your site actually has HTTPS. It won't tell users on HTTP to switch to HTTPS, it will just tell HTTPS users to stick around. You can enforce this with the express-enforces-ssl module. This header is somewhat well-supported by browsers.