Doesn't need an extension to search with a keyword (or a keyletter). In the settings for #Chromium or #Chrome open "Manage search engines", DuckDuckGo should already be in there, then change the keyword from "duckduckgo.com" to "!". Now you can search ddg by typing "! thing-to-search-for" (yes, you do need a space). For !Firefox and its derivates create a new bookmark with the location "https://duckduckgo.com/html?q=%s" and the keyword "!", and again you can search by typing "! stuff"