It's a web interface linked to a service in the cloud. You can't secure a web interface, since the changes going on the backend are invisible to the user and ev

It's a web interface linked to a service in the cloud. You can't secure a web interface, since the changes going on the backend are invisible to the user and even if you have a system that makes use of end to end cryptography (which doesn't apply here), you can always be targeted with a special version of the client that tracks you. This is why online password managers that allow you to insert your password in a web form are inherently insecure. So it would be cool if DDG open sourced their code, but it wouldn't help for doing reviews of how well they respect their privacy policy. In such cases you just have to trust them. Well, for companies such as DDG, if they broke their privacy policy and word got out, the company would go out of business fast. Since a good reputation is all they have.