Force Safe Search web extension
The Force Safe Search extension keeps the safest search options in effect, even when in incognito mode or when the user tries to force the setting to a new value. It works for all major search engines: Google, YouTube, Bing, Yahoo, and DuckDuckGo. This free plug-in is one piece of an effective toolkit for keeping a home or work environment safe from inappropriate content.
Extension for Microsoft Edge and Safari coming soon.