It simply means there's no obvious fingerprint that builtwith.com was able to detect. For example, the default Express app contains `X-Powered-By: Express` in

It simply means there's no obvious fingerprint that builtwith.com was able to detect. For example, the default Express app contains `X-Powered-By: Express` in the response header. Ruby on Rails is usually sniffed by its predictable cookie signature. You gain nothing from broadcasting your back-end stack to the world.