The DNS-over-HTTPS (DoH) protocol is currently the talk of the town, and the Firefox browser is the only one to support it.
However, the feature is not enabled by default for Firefox users, who will have to go through many hoops and modify multiple settings before they can get the DoH up and running.
But before we go into a step-by-step tutorial on how someone can enable DoH support in Firefox, let's describe what it does first.
How DNS-over-HTTPS works
The DNS-over-HTTPS protocol works by taking a domain name that a user has typed in their browser and sending a query to a DNS server to learn the numerical IP address of the web server that hosts that specific site.
This is how normal DNS works, too. However, DoH takes the DNS query and sends it to a DoH-compatible DNS server (resolver) via an encrypted HTTPS connection on port 443, rather than plaintext on port 53.
This way, DoH hides DNS queries inside regular HTTPS traffic, so third-party observers won't be able to sniff traffic and tell what DNS queries users have run and infer what websites they are about to access.
Further, a secondary feature of DNS-over-HTTPS is that the protocol works at the app level. Apps can come with internally hardcoded lists of DoH-compatible DNS resolvers where they can send DoH queries.
This mode of operation bypasses the default DNS settings that exist at the OS level, which, in most cases are the ones set by local internet service providers (ISPs).
This also means that apps that support DoH can effectively bypass local ISPs traffic filters and access content that may be blocked by a local telco or local government -- and a reason why DoH is currently hailed as