YouTube Search Engine Shortcut od James

This add-on adds YouTube to the list of search engine shortcuts in Firefox.

By typing "yt" followed by a space, you are then able to search for videos on YouTube.
For example, after typing in the query "yt funny cats" your tab will redirect you to the search results for funny cats on YouTube.
You can modify the keyword for this extension by going to the Firefox Options -> Search -> Search Shortcuts