DNS is a system that translates domain names into numbered IP addresses. When you type a website address or open an app, DNS is like a digital phone book that makes sure your device connects with the information you’re looking for. If you have consistent DNS resolution, it means that everyone who uses the Internet sees the same things, wherever they are in the world.
An Internet Service Provider (ISP) usually chooses a DNS for its customers, so most users don’t need to think about it. And if there’s an outage or attack, the traffic can be rerouted, making the system resilient.
Some DNS resolvers filter certain domain names that are known to be malicious, such as links to malware. But when DNS resolvers start to filter specific types of content, this poses a threat to the Internet overall. It means that the resolver is no longer just a translator. This creates a scenario where what you can see and do online depends on what DNS resolver is being used—something you don’t always control.