The services DNS are used to "translate" domain names into IP addresses used by computers for communication. The providers DNS are critical to privacy as they know every site that users have access to. Some people use this information for marketing purposes and sell it to the highest bidder.
The default provider DNS is usually the Internet Service Provider, but is often not the fastest or most secure.
For anyone interested DNS benchmarking tools are available that can help you find the best provider, at least in terms of speed.
Η Quad9 therefore made the deliberate decision to transfer its services to Switzerland (Swiss jurisdiction) and therefore to Swiss privacy laws. The move to Switzerland was designed to boost her commitment Quad9 to keep its users' data private and secure.
The company states that all its users will benefit from this move, as "the Swiss Data Protection Act does not contain any restrictions on the citizenship or residence of persons whose personal rights are protected by law." In other words: all its users Quad9 have the same legal protection as Swiss citizens if they use the service.
Users who prefer to use only the service DNS without add-ons should use the IP addresses 18.104.22.168, 22.214.171.124 and 2620: fe :: 10 respectively.
Finally, an ECS-protected variant is also available using the IP addresses 126.96.36.199, 188.8.131.52, and 2620: fe :: 11.
Installation guides for all of the above options are available at official webpage.