Cloudflare 1.1.1.1 Free Public DNS on Ubuntu 18.04

Step 1: Install resolvconf package via Terminal

$ sudo apt-get install resolvconf

Step 2: Edit /etc/resolvconf/resolv.conf.d/head via your favorite text editor and include the following lines:

nameserver 1.1.1.1
nameserver 1.0.0.1
nameserver 2606:4700:4700::1111
nameserver 2606:4700:4700::1001

Step 3: Save the file and restart the resolvconf service:

$ sudo service resolvconf restart

Done! Open your preferred web browser and test.