!Bangs in DuckDuckGo

I learnt yesterday from a friend how to use the !bang feature of the search engine DuckDuckGo, and it's amazing!

I can directly search inside specific sites without having to go on this site first. Since DuckDuckGo is my default search engine, that means typing !npm express will directly get me on the result page of the npm website.

And so on... Anyone can submit their own, which is why there so many (thousands).
That's an amazing feature for power users!