[EDIT: Better clarity and image; 2020-11-04T07:00:00Z]
Yes, you can overwrite the gray text; those merely indicate the broadcasted defaults provided by your local or ISP gateway, which are currently in use.
Even if you are not concerned about security, Cloudflare just flat-out makes your browser queries when entering a domain name much faster.
Cloudflare DNS
Copy the following DNS IP Addresses, one line at a time; then hit the ‘+’ button (see image below); Paste the number in the highlighted field; pressing ‘Enter’ after each entry:
2606:4700:4700::1111
2606:4700:4700::1001
1.1.1.1
1.0.0.1
The first two very long numbers are IPv6, the last two traditional IPv4; modern devices will attempt to use IPv6 first (it’s faster in many cases and “more” secure), then fall back if needed; older devices may not be capable of using IPv6 and will fall back to IPv4.
[NOTE: See below posts for information about named DNS ‘Search Domains’; most people can safely ignore them]
NOTE: if editing a device/Mac, repeat the above procedure for each active connection type and profile (e.g., Ethernet 1, Ethernet 2, Firewire, Bluetooth, [name of each of your common] WiFi Network(s); you will find these settings under the ‘Advanced’ button for each connection type.
NOTE: if you have WiFi extenders providing independent DNS, or just passing along the default DNS from your ISP (as opposed to being in Bridge Mode, where the extenders simply pass requests to your router or gateway), be sure to install the custom DNS on each base station or WiFi router.
You will also note in the above image that I also have Google’s DNS listed after Cloudflare; this is just in case all four of Cloudflare’s DNS Servers go down (unlikely, but things happen); if they don’t respond quickly, your query will fall back to Google’s DNS and avoid the dreaded Unmoving Progress Bar, that once plagued virtually all ISPs; that is, in part, why Google, and FreeDNS, et al, started offering more reliable lookup servers.
Google DNS
2001:4860:4860::8888
2001:4860:4860::8844
8.8.8.8
8.8.4.4
(cf https://www.techradar.com/news/best-dns-server)
I swear, back in the 90s and 00s, my local ISP (Century Link née Qwest née Mountain Bell) had exactly one Pentium II hosting DNS lookup, and when it crashed, no one got anywhere without a numbered IP address. This worldwide phenomena set off the once-popular self-hosted DNS tables; Mac and PC users alike would run trace route
to discover the static IP address for all their frequented sites, and edit their hosts
file; this way your own machine automatically translated domain names to IP addresses in a blink. No more dreaded Unmoving Progress Bar (cf How To Setup A Local DNS Host File On Mac OS X)
You can still do this today, if you wish, of course; there are freeware GUI editors for doing this automatically; at one time there were (and probably still are) browser plugins that automatically and silently edit the hosts
file on the fly.
For iOS users, here’s the easy to use, free for DNS (subscription for VPN data): 1.1.1.1: Faster Internet on the App Store
HTH
Frederico