Level 3
Then as suggested, CloudFlare is popular to be fast (probably because it is still not very popular), it is at: and alternate server

Keep in mind that CloudFlare is uncensored DNS which means it will not block anything either good or bad.

You may also try Quad9 which claims to respect privacy and does filter bad URLs.
You may search this forums for several threads regarding DNS servers and some tests being done on the popular ones.