The best ext in the places vacuum category, cleaning only fewer viewed sites history is the highlight and showing results is a humanized design. But why I gave 4 stars:
Because I found that it does not clean navigation bar history. For example, I set deleting entries viewed 1000 or less, this is supposed to delete all the browsing history, when I click clean, yes it does clean all the history, however, in the navigation bar, when you type some words, they are still there. If you use FF self history cleaning function, it will clean navigation bar history too.
Of course I do not use this ext to clean all the browsing history, but when I tried to do this, I can see this ext does not clean navigation bar history as what I want while FF self cleaning does the right thing.