The Expect-CT HTTP header tells browsers to expect Certificate Transparency. For more about Certificate Transparency and this header, see this blog post and the in-progress spec.

Usage:

var expectCt = require('expect-ct')

// Sets Expect-CT: max-age=123
app.use(expectCt({ maxAge: 123 }))

// Sets Expect-CT: enforce; max-age=123
app.use(expectCt({
  enforce: true,
  maxAge: 123
}))

// Sets Expect-CT: enforce; max-age=30; report-uri="http://example.com/report"
app.use(expectCt({
  enforce: true,
  maxAge: 30,
  reportUri: 'http://example.com/report'
}))